diff --git a/chrome/browser/sync/glue/sync_backend_host.h b/chrome/browser/sync/glue/sync_backend_host.h
index 0ace4140614dff..a2861ef7f57ffe 100644
--- a/chrome/browser/sync/glue/sync_backend_host.h
+++ b/chrome/browser/sync/glue/sync_backend_host.h
@@ -192,6 +192,9 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
   // Fetches the DeviceInfo tracker.
   virtual SyncedDeviceTracker* GetSyncedDeviceTracker() const = 0;
 
+  // Sets whether or not the frontend will be notified of network events.
+  virtual void SetForwardProtocolEvents(bool forward) = 0;
+
   virtual base::MessageLoop* GetSyncLoopForTesting() = 0;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHost);
diff --git a/chrome/browser/sync/glue/sync_backend_host_core.cc b/chrome/browser/sync/glue/sync_backend_host_core.cc
index b6249c9456357d..c433b0b3df9604 100644
--- a/chrome/browser/sync/glue/sync_backend_host_core.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_core.cc
@@ -12,6 +12,7 @@
 #include "chrome/browser/sync/glue/synced_device_tracker.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/chrome_version_info.h"
+#include "sync/internal_api/public/events/protocol_event.h"
 #include "sync/internal_api/public/http_post_provider_factory.h"
 #include "sync/internal_api/public/internal_components_factory.h"
 #include "sync/internal_api/public/sessions/sync_session_snapshot.h"
@@ -316,6 +317,18 @@ void SyncBackendHostCore::OnMigrationRequested(syncer::ModelTypeSet types) {
       types);
 }
 
+void SyncBackendHostCore::OnProtocolEvent(
+    const syncer::ProtocolEvent& event) {
+  // TODO(rlarocque): Find a way to pass event_clone as a scoped_ptr.
+  if (forward_protocol_events_) {
+    scoped_ptr<syncer::ProtocolEvent> event_clone(event.Clone());
+    host_.Call(
+        FROM_HERE,
+        &SyncBackendHostImpl::HandleProtocolEventOnFrontendLoop,
+        event_clone.release());
+  }
+}
+
 void SyncBackendHostCore::DoOnInvalidatorStateChange(
     syncer::InvalidatorState state) {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
@@ -592,6 +605,11 @@ void SyncBackendHostCore::DoRetryConfiguration(
              retry_callback);
 }
 
+void SyncBackendHostCore::SetForwardProtocolEvents(bool enabled) {
+  DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
+  forward_protocol_events_ = enabled;
+}
+
 void SyncBackendHostCore::DeleteSyncDataFolder() {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   if (base::DirectoryExists(sync_data_folder_path_)) {
diff --git a/chrome/browser/sync/glue/sync_backend_host_core.h b/chrome/browser/sync/glue/sync_backend_host_core.h
index d0b9793980d83f..d246255698d09a 100644
--- a/chrome/browser/sync/glue/sync_backend_host_core.h
+++ b/chrome/browser/sync/glue/sync_backend_host_core.h
@@ -102,6 +102,7 @@ class SyncBackendHostCore
   virtual void OnActionableError(
       const syncer::SyncProtocolError& sync_error) OVERRIDE;
   virtual void OnMigrationRequested(syncer::ModelTypeSet types) OVERRIDE;
+  virtual void OnProtocolEvent(const syncer::ProtocolEvent& event) OVERRIDE;
 
   // SyncEncryptionHandler::Observer implementation.
   virtual void OnPassphraseRequired(
@@ -208,6 +209,8 @@ class SyncBackendHostCore
     return synced_device_tracker_.get();
   }
 
+  void SetForwardProtocolEvents(bool forward);
+
   // Delete the sync data folder to cleanup backend data.  Happens the first
   // time sync is enabled for a user (to prevent accidentally reusing old
   // sync databases), as well as shutdown when you're no longer syncing.
@@ -285,6 +288,9 @@ class SyncBackendHostCore
   // Should not be used for anything except for UMAs and logging.
   const bool has_sync_setup_completed_;
 
+  // Set when we've been asked to forward sync protocol events to the frontend.
+  bool forward_protocol_events_;
+
   base::WeakPtrFactory<SyncBackendHostCore> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHostCore);
diff --git a/chrome/browser/sync/glue/sync_backend_host_impl.cc b/chrome/browser/sync/glue/sync_backend_host_impl.cc
index f5b2f6e4677bd9..de87a4939a3725 100644
--- a/chrome/browser/sync/glue/sync_backend_host_impl.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_impl.cc
@@ -19,6 +19,7 @@
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_source.h"
 #include "sync/internal_api/public/base_transaction.h"
+#include "sync/internal_api/public/events/protocol_event.h"
 #include "sync/internal_api/public/http_bridge.h"
 #include "sync/internal_api/public/internal_components_factory.h"
 #include "sync/internal_api/public/internal_components_factory_impl.h"
@@ -474,6 +475,14 @@ SyncedDeviceTracker* SyncBackendHostImpl::GetSyncedDeviceTracker() const {
   return core_->synced_device_tracker();
 }
 
+void SyncBackendHostImpl::SetForwardProtocolEvents(bool forward) {
+  DCHECK(initialized());
+  registrar_->sync_thread()->message_loop()->PostTask(
+      FROM_HERE,
+      base::Bind(&SyncBackendHostCore::SetForwardProtocolEvents,
+                 core_, forward));
+}
+
 void SyncBackendHostImpl::InitCore(scoped_ptr<DoInitializeOptions> options) {
   registrar_->sync_thread()->message_loop()->PostTask(FROM_HERE,
       base::Bind(&SyncBackendHostCore::DoInitialize,
@@ -744,6 +753,14 @@ void SyncBackendHostImpl::HandleConnectionStatusChangeOnFrontendLoop(
   frontend_->OnConnectionStatusChange(status);
 }
 
+void SyncBackendHostImpl::HandleProtocolEventOnFrontendLoop(
+    syncer::ProtocolEvent* event) {
+  scoped_ptr<syncer::ProtocolEvent> scoped_event(event);
+  if (!frontend_)
+    return;
+  frontend_->OnProtocolEvent(*scoped_event);
+}
+
 base::MessageLoop* SyncBackendHostImpl::GetSyncLoopForTesting() {
   return registrar_->sync_thread()->message_loop();
 }
diff --git a/chrome/browser/sync/glue/sync_backend_host_impl.h b/chrome/browser/sync/glue/sync_backend_host_impl.h
index b2ed9627cd9436..24e621513239c4 100644
--- a/chrome/browser/sync/glue/sync_backend_host_impl.h
+++ b/chrome/browser/sync/glue/sync_backend_host_impl.h
@@ -124,6 +124,7 @@ class SyncBackendHostImpl
   virtual void GetModelSafeRoutingInfo(
       syncer::ModelSafeRoutingInfo* out) const OVERRIDE;
   virtual SyncedDeviceTracker* GetSyncedDeviceTracker() const OVERRIDE;
+  virtual void SetForwardProtocolEvents(bool forward) OVERRIDE;
   virtual base::MessageLoop* GetSyncLoopForTesting() OVERRIDE;
 
  protected:
@@ -166,6 +167,11 @@ class SyncBackendHostImpl
   // frontend's sync configure retry method.
   void HandleControlTypesDownloadRetry();
 
+  // Forwards a ProtocolEvent to the frontend.  Will not be called unless a
+  // call to SetForwardProtocolEvents() explicitly requested that we start
+  // forwarding these events.
+  void HandleProtocolEventOnFrontendLoop(syncer::ProtocolEvent* event);
+
   SyncFrontend* frontend() { return frontend_; }
 
  private:
diff --git a/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc b/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
index 62553d15cbb99e..add3e2c5a88dbc 100644
--- a/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
@@ -82,6 +82,7 @@ class MockSyncFrontend : public SyncFrontend {
                void(syncer::ModelTypeSet, bool));
   MOCK_METHOD0(OnEncryptionComplete, void());
   MOCK_METHOD1(OnMigrationNeededForTypes, void(syncer::ModelTypeSet));
+  MOCK_METHOD1(OnProtocolEvent, void(const syncer::ProtocolEvent&));
   MOCK_METHOD1(OnExperimentsChanged,
       void(const syncer::Experiments&));
   MOCK_METHOD1(OnActionableError,
diff --git a/chrome/browser/sync/glue/sync_backend_host_mock.cc b/chrome/browser/sync/glue/sync_backend_host_mock.cc
index 7f219351a7a753..f7629b22227d2c 100644
--- a/chrome/browser/sync/glue/sync_backend_host_mock.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_mock.cc
@@ -110,6 +110,8 @@ base::MessageLoop* SyncBackendHostMock::GetSyncLoopForTesting() {
   return NULL;
 }
 
+void SyncBackendHostMock::SetForwardProtocolEvents(bool enabled) {}
+
 void SyncBackendHostMock::set_fail_initial_download(bool should_fail) {
   fail_initial_download_ = should_fail;
 }
diff --git a/chrome/browser/sync/glue/sync_backend_host_mock.h b/chrome/browser/sync/glue/sync_backend_host_mock.h
index fb90c2bafb09c1..b75a0879b69849 100644
--- a/chrome/browser/sync/glue/sync_backend_host_mock.h
+++ b/chrome/browser/sync/glue/sync_backend_host_mock.h
@@ -93,6 +93,8 @@ class SyncBackendHostMock : public SyncBackendHost {
 
   virtual SyncedDeviceTracker* GetSyncedDeviceTracker() const OVERRIDE;
 
+  virtual void SetForwardProtocolEvents(bool enabled) OVERRIDE;
+
   virtual base::MessageLoop* GetSyncLoopForTesting() OVERRIDE;
 
   void set_fail_initial_download(bool should_fail);
diff --git a/chrome/browser/sync/profile_sync_service.cc b/chrome/browser/sync/profile_sync_service.cc
index 616c2bb45bcddd..57f6c2cf96fe70 100644
--- a/chrome/browser/sync/profile_sync_service.cc
+++ b/chrome/browser/sync/profile_sync_service.cc
@@ -562,6 +562,13 @@ void ProfileSyncService::OnSyncConfigureRetry() {
   NotifyObservers();
 }
 
+void ProfileSyncService::OnProtocolEvent(
+    const syncer::ProtocolEvent& event) {
+  FOR_EACH_OBSERVER(browser_sync::ProtocolEventObserver,
+                    protocol_event_observers_,
+                    OnProtocolEvent(event));
+}
+
 void ProfileSyncService::OnDataTypeRequestsSyncStartup(
     syncer::ModelType type) {
   DCHECK(syncer::UserTypes().Has(type));
@@ -936,6 +943,10 @@ void ProfileSyncService::OnBackendInitialized(
   sync_js_controller_.AttachJsBackend(js_backend);
   debug_info_listener_ = debug_info_listener;
 
+  if (protocol_event_observers_.might_have_observers()) {
+    backend_->SetForwardProtocolEvents(true);
+  }
+
   // If we have a cached passphrase use it to decrypt/encrypt data now that the
   // backend is initialized. We want to call this before notifying observers in
   // case this operation affects the "passphrase required" status.
@@ -2070,6 +2081,24 @@ void ProfileSyncService::RemoveObserver(
   observers_.RemoveObserver(observer);
 }
 
+void ProfileSyncService::AddProtocolEventObserver(
+    browser_sync::ProtocolEventObserver* observer) {
+  protocol_event_observers_.AddObserver(observer);
+  if (backend_) {
+    backend_->SetForwardProtocolEvents(
+        protocol_event_observers_.might_have_observers());
+  }
+}
+
+void ProfileSyncService::RemoveProtocolEventObserver(
+    browser_sync::ProtocolEventObserver* observer) {
+  protocol_event_observers_.RemoveObserver(observer);
+  if (backend_) {
+    backend_->SetForwardProtocolEvents(
+        protocol_event_observers_.might_have_observers());
+  }
+}
+
 bool ProfileSyncService::HasObserver(
     ProfileSyncServiceBase::Observer* observer) const {
   return observers_.HasObserver(observer);
diff --git a/chrome/browser/sync/profile_sync_service.h b/chrome/browser/sync/profile_sync_service.h
index 0b3c439a5e8124..cdffa0b38f4a15 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -25,6 +25,7 @@
 #include "chrome/browser/sync/glue/synced_device_tracker.h"
 #include "chrome/browser/sync/profile_sync_service_base.h"
 #include "chrome/browser/sync/profile_sync_service_observer.h"
+#include "chrome/browser/sync/protocol_event_observer.h"
 #include "chrome/browser/sync/sessions2/sessions_sync_manager.h"
 #include "chrome/browser/sync/startup_controller.h"
 #include "components/keyed_service/core/keyed_service.h"
@@ -273,6 +274,11 @@ class ProfileSyncService : public ProfileSyncServiceBase,
   virtual bool HasObserver(
       ProfileSyncServiceBase::Observer* observer) const OVERRIDE;
 
+
+  void AddProtocolEventObserver(browser_sync::ProtocolEventObserver* observer);
+  void RemoveProtocolEventObserver(
+      browser_sync::ProtocolEventObserver* observer);
+
   void RegisterAuthNotifications();
   void UnregisterAuthNotifications();
 
@@ -365,6 +371,7 @@ class ProfileSyncService : public ProfileSyncServiceBase,
           debug_info_listener,
       bool success) OVERRIDE;
   virtual void OnSyncCycleCompleted() OVERRIDE;
+  virtual void OnProtocolEvent(const syncer::ProtocolEvent& event) OVERRIDE;
   virtual void OnSyncConfigureRetry() OVERRIDE;
   virtual void OnConnectionStatusChange(
       syncer::ConnectionStatus status) OVERRIDE;
@@ -911,6 +918,7 @@ class ProfileSyncService : public ProfileSyncServiceBase,
   scoped_ptr<browser_sync::DataTypeManager> data_type_manager_;
 
   ObserverList<ProfileSyncServiceBase::Observer> observers_;
+  ObserverList<browser_sync::ProtocolEventObserver> protocol_event_observers_;
 
   syncer::SyncJsController sync_js_controller_;
 
diff --git a/chrome/browser/sync/protocol_event_observer.cc b/chrome/browser/sync/protocol_event_observer.cc
new file mode 100644
index 00000000000000..b9079078a42748
--- /dev/null
+++ b/chrome/browser/sync/protocol_event_observer.cc
@@ -0,0 +1,13 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/sync/protocol_event_observer.h"
+
+namespace browser_sync {
+
+ProtocolEventObserver::ProtocolEventObserver() {}
+
+ProtocolEventObserver::~ProtocolEventObserver() {}
+
+}  // namespace browser_sync
diff --git a/chrome/browser/sync/protocol_event_observer.h b/chrome/browser/sync/protocol_event_observer.h
new file mode 100644
index 00000000000000..3ed4095fb72990
--- /dev/null
+++ b/chrome/browser/sync/protocol_event_observer.h
@@ -0,0 +1,24 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_SYNC_PROTOCOL_EVENT_OBSERVER_H_
+#define CHROME_BROWSER_SYNC_PROTOCOL_EVENT_OBSERVER_H_
+
+namespace syncer {
+class ProtocolEvent;
+}
+
+namespace browser_sync {
+
+class ProtocolEventObserver {
+ public:
+  ProtocolEventObserver();
+  virtual ~ProtocolEventObserver();
+
+  virtual void OnProtocolEvent(const syncer::ProtocolEvent& event) = 0;
+};
+
+}  // namespace browser_sync
+
+#endif  // CHROME_BROWSER_SYNC_PROTOCOL_EVENT_OBSERVER_H_
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index 295efb63d64dd7..ef9bedfed104d2 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -2360,6 +2360,8 @@
         'browser/sync/profile_sync_service_model_type_selection_android.h',
         'browser/sync/profile_sync_service_observer.cc',
         'browser/sync/profile_sync_service_observer.h',
+        'browser/sync/protocol_event_observer.cc',
+        'browser/sync/protocol_event_observer.h',
         'browser/sync/sessions2/notification_service_sessions_router.cc',
         'browser/sync/sessions2/notification_service_sessions_router.h',
         'browser/sync/sessions2/session_data_type_controller2.cc',
diff --git a/components/sync_driver/sync_frontend.h b/components/sync_driver/sync_frontend.h
index f7ed853d50bd3a..47d76bead8a124 100644
--- a/components/sync_driver/sync_frontend.h
+++ b/components/sync_driver/sync_frontend.h
@@ -15,6 +15,7 @@
 namespace syncer {
 class DataTypeDebugInfoListener;
 class JsBackend;
+class ProtocolEvent;
 }  // namespace syncer
 
 namespace sync_pb {
@@ -53,6 +54,14 @@ class SyncFrontend {
   // retried.
   virtual void OnSyncConfigureRetry() = 0;
 
+  // Informs the frontned of some network event.  These notifications are
+  // disabled by default and must be enabled through an explicit request to the
+  // SyncBackendHost.
+  //
+  // It's disabld by default to avoid copying data across threads when no one
+  // is listening for it.
+  virtual void OnProtocolEvent(const syncer::ProtocolEvent& event) = 0;
+
   // The status of the connection to the sync server has changed.
   virtual void OnConnectionStatusChange(
       syncer::ConnectionStatus status) = 0;
diff --git a/sync/engine/DEPS b/sync/engine/DEPS
index b43d31c6cd0310..097869789fd1e8 100644
--- a/sync/engine/DEPS
+++ b/sync/engine/DEPS
@@ -2,6 +2,7 @@ include_rules = [
   "+sync/base",
   "+sync/internal_api/public/base",
   "+sync/internal_api/public/engine",
+  "+sync/internal_api/public/events",
   "+sync/internal_api/public/sessions",
   "+sync/internal_api/public/test",
   "+sync/internal_api/public/util",
diff --git a/sync/engine/all_status.cc b/sync/engine/all_status.cc
index 6fa98d35c538af..d73f206eae9afa 100644
--- a/sync/engine/all_status.cc
+++ b/sync/engine/all_status.cc
@@ -124,6 +124,8 @@ void AllStatus::OnThrottledTypesChanged(ModelTypeSet throttled_types) {
 
 void AllStatus::OnMigrationRequested(ModelTypeSet) {}
 
+void AllStatus::OnProtocolEvent(const ProtocolEvent&) {}
+
 SyncStatus AllStatus::status() const {
   base::AutoLock lock(mutex_);
   return status_;
diff --git a/sync/engine/all_status.h b/sync/engine/all_status.h
index add42e5b30053f..999f2f36449f53 100644
--- a/sync/engine/all_status.h
+++ b/sync/engine/all_status.h
@@ -46,6 +46,7 @@ class AllStatus : public SyncEngineEventListener {
   virtual void OnRetryTimeChanged(base::Time retry_time) OVERRIDE;
   virtual void OnThrottledTypesChanged(ModelTypeSet throttled_types) OVERRIDE;
   virtual void OnMigrationRequested(ModelTypeSet types) OVERRIDE;
+  virtual void OnProtocolEvent(const ProtocolEvent& event) OVERRIDE;
 
   SyncStatus status() const;
 
diff --git a/sync/engine/commit.cc b/sync/engine/commit.cc
index 90b97427025fff..92cf4d2aa776fd 100644
--- a/sync/engine/commit.cc
+++ b/sync/engine/commit.cc
@@ -10,6 +10,8 @@
 #include "sync/engine/commit_util.h"
 #include "sync/engine/syncer.h"
 #include "sync/engine/syncer_proto_util.h"
+#include "sync/internal_api/public/events/commit_request_event.h"
+#include "sync/internal_api/public/events/commit_response_event.h"
 #include "sync/sessions/sync_session.h"
 
 namespace syncer {
@@ -97,11 +99,26 @@ SyncerError Commit::PostAndProcessResponse(
   }
 
   DVLOG(1) << "Sending commit message.";
+
+  CommitRequestEvent request_event(
+      base::Time::Now(),
+      message_.commit().entries_size(),
+      request_types,
+      message_);
+  session->SendProtocolEvent(request_event);
+
   TRACE_EVENT_BEGIN0("sync", "PostCommit");
   const SyncerError post_result = SyncerProtoUtil::PostClientToServerMessage(
       &message_, &response_, session);
   TRACE_EVENT_END0("sync", "PostCommit");
 
+  // TODO(rlarocque): Use result that includes errors captured later?
+  CommitResponseEvent response_event(
+      base::Time::Now(),
+      post_result,
+      response_);
+  session->SendProtocolEvent(response_event);
+
   if (post_result != SYNCER_OK) {
     LOG(WARNING) << "Post commit failed";
     return post_result;
diff --git a/sync/engine/get_updates_delegate.cc b/sync/engine/get_updates_delegate.cc
index 4697485b52f9de..fe538412ea8297 100644
--- a/sync/engine/get_updates_delegate.cc
+++ b/sync/engine/get_updates_delegate.cc
@@ -6,6 +6,9 @@
 
 #include "sync/engine/directory_update_handler.h"
 #include "sync/engine/get_updates_processor.h"
+#include "sync/internal_api/public/events/configure_get_updates_request_event.h"
+#include "sync/internal_api/public/events/normal_get_updates_request_event.h"
+#include "sync/internal_api/public/events/poll_get_updates_request_event.h"
 
 namespace syncer {
 
@@ -80,6 +83,13 @@ void NormalGetUpdatesDelegate::ApplyUpdates(
   NonPassiveApplyUpdates(status_controller, update_handler_map);
 }
 
+scoped_ptr<ProtocolEvent> NormalGetUpdatesDelegate::GetNetworkRequestEvent(
+    base::Time timestamp,
+    const sync_pb::ClientToServerMessage& request) const {
+  return scoped_ptr<ProtocolEvent>(
+      new NormalGetUpdatesRequestEvent(timestamp, nudge_tracker_, request));
+}
+
 ConfigureGetUpdatesDelegate::ConfigureGetUpdatesDelegate(
     sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source) : source_(source) {}
 
@@ -97,6 +107,16 @@ void ConfigureGetUpdatesDelegate::ApplyUpdates(
   PassiveApplyUpdates(status_controller, update_handler_map);
 }
 
+scoped_ptr<ProtocolEvent> ConfigureGetUpdatesDelegate::GetNetworkRequestEvent(
+    base::Time timestamp,
+    const sync_pb::ClientToServerMessage& request) const {
+  return scoped_ptr<ProtocolEvent>(
+      new ConfigureGetUpdatesRequestEvent(
+          timestamp,
+          ConvertConfigureSourceToOrigin(source_),
+          request));
+}
+
 sync_pb::SyncEnums::GetUpdatesOrigin
 ConfigureGetUpdatesDelegate::ConvertConfigureSourceToOrigin(
     sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source) {
@@ -136,4 +156,11 @@ void PollGetUpdatesDelegate::ApplyUpdates(
   NonPassiveApplyUpdates(status_controller, update_handler_map);
 }
 
+scoped_ptr<ProtocolEvent> PollGetUpdatesDelegate::GetNetworkRequestEvent(
+    base::Time timestamp,
+    const sync_pb::ClientToServerMessage& request) const {
+  return scoped_ptr<ProtocolEvent>(
+      new PollGetUpdatesRequestEvent(timestamp, request));
+}
+
 }  // namespace syncer
diff --git a/sync/engine/get_updates_delegate.h b/sync/engine/get_updates_delegate.h
index 9ebc6d8fc7b46f..d897edfbcd05ab 100644
--- a/sync/engine/get_updates_delegate.h
+++ b/sync/engine/get_updates_delegate.h
@@ -5,6 +5,7 @@
 #ifndef SYNC_ENGINE_GET_UPDATES_DELEGATE_H_
 #define SYNC_ENGINE_GET_UPDATES_DELEGATE_H_
 
+#include "sync/internal_api/public/events/protocol_event.h"
 #include "sync/protocol/sync.pb.h"
 #include "sync/sessions/model_type_registry.h"
 #include "sync/sessions/nudge_tracker.h"
@@ -31,6 +32,10 @@ class SYNC_EXPORT_PRIVATE GetUpdatesDelegate {
   virtual void ApplyUpdates(
       sessions::StatusController* session,
       UpdateHandlerMap* update_handler_map) const = 0;
+
+  virtual scoped_ptr<ProtocolEvent> GetNetworkRequestEvent(
+      base::Time timestamp,
+      const sync_pb::ClientToServerMessage& request) const = 0;
 };
 
 // Functionality specific to the normal GetUpdate request.
@@ -48,6 +53,9 @@ class SYNC_EXPORT_PRIVATE NormalGetUpdatesDelegate : public GetUpdatesDelegate {
       sessions::StatusController* status,
       UpdateHandlerMap* update_handler_map) const OVERRIDE;
 
+  virtual scoped_ptr<ProtocolEvent> GetNetworkRequestEvent(
+      base::Time timestamp,
+      const sync_pb::ClientToServerMessage& request) const OVERRIDE;
  private:
   DISALLOW_COPY_AND_ASSIGN(NormalGetUpdatesDelegate);
 
@@ -74,6 +82,9 @@ class SYNC_EXPORT_PRIVATE ConfigureGetUpdatesDelegate
       sessions::StatusController* status,
       UpdateHandlerMap* update_handler_map) const OVERRIDE;
 
+  virtual scoped_ptr<ProtocolEvent> GetNetworkRequestEvent(
+      base::Time timestamp,
+      const sync_pb::ClientToServerMessage& request) const OVERRIDE;
  private:
   DISALLOW_COPY_AND_ASSIGN(ConfigureGetUpdatesDelegate);
 
@@ -98,6 +109,9 @@ class SYNC_EXPORT_PRIVATE PollGetUpdatesDelegate : public GetUpdatesDelegate {
       sessions::StatusController* status,
       UpdateHandlerMap* update_handler_map) const OVERRIDE;
 
+  virtual scoped_ptr<ProtocolEvent> GetNetworkRequestEvent(
+      base::Time timestamp,
+      const sync_pb::ClientToServerMessage& request) const OVERRIDE;
  private:
   DISALLOW_COPY_AND_ASSIGN(PollGetUpdatesDelegate);
 };
diff --git a/sync/engine/get_updates_processor.cc b/sync/engine/get_updates_processor.cc
index 399c78c714e62b..a5ab59b60fd36c 100644
--- a/sync/engine/get_updates_processor.cc
+++ b/sync/engine/get_updates_processor.cc
@@ -10,6 +10,7 @@
 #include "sync/engine/get_updates_delegate.h"
 #include "sync/engine/syncer_proto_util.h"
 #include "sync/engine/update_handler.h"
+#include "sync/internal_api/public/events/get_updates_response_event.h"
 #include "sync/protocol/sync.pb.h"
 #include "sync/sessions/status_controller.h"
 #include "sync/sessions/sync_session.h"
@@ -193,6 +194,9 @@ SyncerError GetUpdatesProcessor::ExecuteDownloadUpdates(
     CopyClientDebugInfo(session->context()->debug_info_getter(), debug_info);
   }
 
+  session->SendProtocolEvent(
+      *(delegate_.GetNetworkRequestEvent(base::Time::Now(), *msg)));
+
   SyncerError result = SyncerProtoUtil::PostClientToServerMessage(
       msg,
       &update_response,
@@ -202,6 +206,10 @@ SyncerError GetUpdatesProcessor::ExecuteDownloadUpdates(
       update_response);
 
   if (result != SYNCER_OK) {
+    GetUpdatesResponseEvent response_event(
+        base::Time::Now(), update_response, result);
+    session->SendProtocolEvent(response_event);
+
     LOG(ERROR) << "PostClientToServerMessage() failed during GetUpdates";
     return result;
   }
@@ -225,9 +233,15 @@ SyncerError GetUpdatesProcessor::ExecuteDownloadUpdates(
         HandleGetEncryptionKeyResponse(update_response, dir));
   }
 
-  return ProcessResponse(update_response.get_updates(),
-                         request_types,
-                         status);
+  SyncerError process_result = ProcessResponse(update_response.get_updates(),
+                                              request_types,
+                                              status);
+
+  GetUpdatesResponseEvent response_event(
+      base::Time::Now(), update_response, process_result);
+  session->SendProtocolEvent(response_event);
+
+  return process_result;
 }
 
 SyncerError GetUpdatesProcessor::ProcessResponse(
diff --git a/sync/engine/sync_engine_event_listener.h b/sync/engine/sync_engine_event_listener.h
index 35fc05e8ce956d..d5678a92a5edf3 100644
--- a/sync/engine/sync_engine_event_listener.h
+++ b/sync/engine/sync_engine_event_listener.h
@@ -13,6 +13,7 @@ namespace syncer {
 
 struct SyncProtocolError;
 struct SyncCycleEvent;
+class ProtocolEvent;
 
 class SYNC_EXPORT_PRIVATE SyncEngineEventListener {
  public:
@@ -36,6 +37,9 @@ class SYNC_EXPORT_PRIVATE SyncEngineEventListener {
   // This event is sent when the server requests a migration.
   virtual void OnMigrationRequested(ModelTypeSet migration_types) = 0;
 
+  // Emits events when sync communicates with the server.
+  virtual void OnProtocolEvent(const ProtocolEvent& event) = 0;
+
  protected:
   virtual ~SyncEngineEventListener();
 };
diff --git a/sync/engine/sync_scheduler_impl.cc b/sync/engine/sync_scheduler_impl.cc
index a9c635979445b6..2240cd6a0987b7 100644
--- a/sync/engine/sync_scheduler_impl.cc
+++ b/sync/engine/sync_scheduler_impl.cc
@@ -744,6 +744,7 @@ void SyncSchedulerImpl::Unthrottle() {
   // We're no longer throttled, so clear the wait interval.
   wait_interval_.reset();
   NotifyRetryTime(base::Time());
+  NotifyThrottledTypesChanged(nudge_tracker_.GetThrottledTypes());
 
   // We treat this as a 'canary' in the sense that it was originally scheduled
   // to run some time ago, failed, and we now want to retry, versus a job that
@@ -815,6 +816,7 @@ void SyncSchedulerImpl::OnThrottled(const base::TimeDelta& throttle_duration) {
   wait_interval_.reset(new WaitInterval(WaitInterval::THROTTLED,
                                         throttle_duration));
   NotifyRetryTime(base::Time::Now() + wait_interval_->length);
+  NotifyThrottledTypesChanged(ModelTypeSet::All());
 }
 
 void SyncSchedulerImpl::OnTypesThrottled(
diff --git a/sync/engine/syncer_proto_util_unittest.cc b/sync/engine/syncer_proto_util_unittest.cc
index d43b350b346e61..93f9088f6a8888 100644
--- a/sync/engine/syncer_proto_util_unittest.cc
+++ b/sync/engine/syncer_proto_util_unittest.cc
@@ -39,13 +39,11 @@ class MockDelegate : public sessions::SyncSession::Delegate {
    MockDelegate() {}
    ~MockDelegate() {}
 
-  MOCK_METHOD0(IsSyncingCurrentlySilenced, bool());
   MOCK_METHOD1(OnReceivedShortPollIntervalUpdate, void(const base::TimeDelta&));
   MOCK_METHOD1(OnReceivedLongPollIntervalUpdate ,void(const base::TimeDelta&));
   MOCK_METHOD1(OnReceivedSessionsCommitDelay, void(const base::TimeDelta&));
   MOCK_METHOD1(OnReceivedClientInvalidationHintBufferSize, void(int));
   MOCK_METHOD1(OnSyncProtocolError, void(const SyncProtocolError&));
-  MOCK_METHOD1(OnSilencedUntil, void(const base::TimeTicks&));
 };
 
 // Builds a ClientToServerResponse with some data type ids, including
diff --git a/sync/engine/syncer_unittest.cc b/sync/engine/syncer_unittest.cc
index d0a2ab4f4262a5..7a3afe317e2207 100644
--- a/sync/engine/syncer_unittest.cc
+++ b/sync/engine/syncer_unittest.cc
@@ -152,6 +152,7 @@ class SyncerTest : public testing::Test,
   }
   virtual void OnReceivedGuRetryDelay(const base::TimeDelta& delay) OVERRIDE {}
   virtual void OnReceivedMigrationRequest(ModelTypeSet types) OVERRIDE {}
+  virtual void OnProtocolEvent(const ProtocolEvent& event) OVERRIDE {}
   virtual void OnSyncProtocolError(const SyncProtocolError& error) OVERRIDE {}
 
   void GetModelSafeRoutingInfo(ModelSafeRoutingInfo* out) {
diff --git a/sync/internal_api/debug_info_event_listener.cc b/sync/internal_api/debug_info_event_listener.cc
index 6319a03cacf43d..b3d55056eb77f3 100644
--- a/sync/internal_api/debug_info_event_listener.cc
+++ b/sync/internal_api/debug_info_event_listener.cc
@@ -118,6 +118,8 @@ void DebugInfoEventListener::OnActionableError(
 
 void DebugInfoEventListener::OnMigrationRequested(ModelTypeSet types) {}
 
+void DebugInfoEventListener::OnProtocolEvent(const ProtocolEvent& event) {}
+
 void DebugInfoEventListener::OnNudgeFromDatatype(ModelType datatype) {
   DCHECK(thread_checker_.CalledOnValidThread());
   sync_pb::DebugEventInfo event_info;
diff --git a/sync/internal_api/debug_info_event_listener.h b/sync/internal_api/debug_info_event_listener.h
index d9a77c75a94e61..1f716825f09c35 100644
--- a/sync/internal_api/debug_info_event_listener.h
+++ b/sync/internal_api/debug_info_event_listener.h
@@ -51,6 +51,7 @@ class SYNC_EXPORT_PRIVATE DebugInfoEventListener
   virtual void OnActionableError(
       const SyncProtocolError& sync_error) OVERRIDE;
   virtual void OnMigrationRequested(ModelTypeSet types) OVERRIDE;
+  virtual void OnProtocolEvent(const ProtocolEvent& event) OVERRIDE;
 
   // SyncEncryptionHandler::Observer implementation.
   virtual void OnPassphraseRequired(
diff --git a/sync/internal_api/events/commit_request_event.cc b/sync/internal_api/events/commit_request_event.cc
index bed23d3c6bc386..0a1de1f56d415b 100644
--- a/sync/internal_api/events/commit_request_event.cc
+++ b/sync/internal_api/events/commit_request_event.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/internal_api/events/commit_request_event.h"
+#include "sync/internal_api/public/events/commit_request_event.h"
 
 #include "base/format_macros.h"
 #include "base/strings/stringprintf.h"
diff --git a/sync/internal_api/events/commit_response_event.cc b/sync/internal_api/events/commit_response_event.cc
index ec51f5e9107b3c..c263e944adb3fb 100644
--- a/sync/internal_api/events/commit_response_event.cc
+++ b/sync/internal_api/events/commit_response_event.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/internal_api/events/commit_response_event.h"
+#include "sync/internal_api/public/events/commit_response_event.h"
 
 #include "base/strings/stringprintf.h"
 #include "sync/protocol/proto_value_conversions.h"
diff --git a/sync/internal_api/events/configure_get_updates_request_event.cc b/sync/internal_api/events/configure_get_updates_request_event.cc
index 252ae0a9a3aecd..8b487b60c862e5 100644
--- a/sync/internal_api/events/configure_get_updates_request_event.cc
+++ b/sync/internal_api/events/configure_get_updates_request_event.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/internal_api/events/configure_get_updates_request_event.h"
+#include "sync/internal_api/public/events/configure_get_updates_request_event.h"
 
 #include "base/strings/stringprintf.h"
 #include "sync/protocol/proto_enum_conversions.h"
diff --git a/sync/internal_api/events/get_updates_response_event.cc b/sync/internal_api/events/get_updates_response_event.cc
index 17c0e8e50a410a..50bc551900fb95 100644
--- a/sync/internal_api/events/get_updates_response_event.cc
+++ b/sync/internal_api/events/get_updates_response_event.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/internal_api/events/get_updates_response_event.h"
+#include "sync/internal_api/public/events/get_updates_response_event.h"
 
 #include "base/strings/stringprintf.h"
 #include "sync/protocol/proto_value_conversions.h"
diff --git a/sync/internal_api/events/normal_get_updates_request_event.cc b/sync/internal_api/events/normal_get_updates_request_event.cc
index d6a2f884431aae..f5d6cd4112e24c 100644
--- a/sync/internal_api/events/normal_get_updates_request_event.cc
+++ b/sync/internal_api/events/normal_get_updates_request_event.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/internal_api/events/normal_get_updates_request_event.h"
+#include "sync/internal_api/public/events/normal_get_updates_request_event.h"
 
 #include "base/strings/stringprintf.h"
 #include "sync/protocol/proto_value_conversions.h"
diff --git a/sync/internal_api/events/poll_get_updates_request_event.cc b/sync/internal_api/events/poll_get_updates_request_event.cc
index 802d4cbed1179a..c6eecb9807459f 100644
--- a/sync/internal_api/events/poll_get_updates_request_event.cc
+++ b/sync/internal_api/events/poll_get_updates_request_event.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/internal_api/events/poll_get_updates_request_event.h"
+#include "sync/internal_api/public/events/poll_get_updates_request_event.h"
 
 #include "sync/protocol/proto_value_conversions.h"
 
diff --git a/sync/internal_api/js_sync_manager_observer.cc b/sync/internal_api/js_sync_manager_observer.cc
index 57df9d3e340b59..b5f84524ad98e7 100644
--- a/sync/internal_api/js_sync_manager_observer.cc
+++ b/sync/internal_api/js_sync_manager_observer.cc
@@ -60,6 +60,9 @@ void JsSyncManagerObserver::OnActionableError(
                 JsEventDetails(&details));
 }
 
+void JsSyncManagerObserver::OnProtocolEvent(
+    const ProtocolEvent& event) { }
+
 void JsSyncManagerObserver::OnMigrationRequested(ModelTypeSet types) { }
 
 void JsSyncManagerObserver::OnInitializationComplete(
diff --git a/sync/internal_api/js_sync_manager_observer.h b/sync/internal_api/js_sync_manager_observer.h
index a30a40bbd8a5c9..6f220054b7671b 100644
--- a/sync/internal_api/js_sync_manager_observer.h
+++ b/sync/internal_api/js_sync_manager_observer.h
@@ -42,6 +42,7 @@ class SYNC_EXPORT_PRIVATE JsSyncManagerObserver : public SyncManager::Observer {
       syncer::ModelTypeSet restored_types) OVERRIDE;
   virtual void OnActionableError(
       const SyncProtocolError& sync_protocol_error) OVERRIDE;
+  virtual void OnProtocolEvent(const ProtocolEvent& event) OVERRIDE;
   virtual void OnMigrationRequested(
       syncer::ModelTypeSet types) OVERRIDE;
 
diff --git a/sync/internal_api/events/commit_request_event.h b/sync/internal_api/public/events/commit_request_event.h
similarity index 100%
rename from sync/internal_api/events/commit_request_event.h
rename to sync/internal_api/public/events/commit_request_event.h
diff --git a/sync/internal_api/events/commit_response_event.h b/sync/internal_api/public/events/commit_response_event.h
similarity index 100%
rename from sync/internal_api/events/commit_response_event.h
rename to sync/internal_api/public/events/commit_response_event.h
diff --git a/sync/internal_api/events/configure_get_updates_request_event.h b/sync/internal_api/public/events/configure_get_updates_request_event.h
similarity index 100%
rename from sync/internal_api/events/configure_get_updates_request_event.h
rename to sync/internal_api/public/events/configure_get_updates_request_event.h
diff --git a/sync/internal_api/events/get_updates_response_event.h b/sync/internal_api/public/events/get_updates_response_event.h
similarity index 100%
rename from sync/internal_api/events/get_updates_response_event.h
rename to sync/internal_api/public/events/get_updates_response_event.h
diff --git a/sync/internal_api/events/normal_get_updates_request_event.h b/sync/internal_api/public/events/normal_get_updates_request_event.h
similarity index 100%
rename from sync/internal_api/events/normal_get_updates_request_event.h
rename to sync/internal_api/public/events/normal_get_updates_request_event.h
diff --git a/sync/internal_api/events/poll_get_updates_request_event.h b/sync/internal_api/public/events/poll_get_updates_request_event.h
similarity index 100%
rename from sync/internal_api/events/poll_get_updates_request_event.h
rename to sync/internal_api/public/events/poll_get_updates_request_event.h
diff --git a/sync/internal_api/public/sync_manager.h b/sync/internal_api/public/sync_manager.h
index fa2e58511f2dac..6f6d9fc0a1b517 100644
--- a/sync/internal_api/public/sync_manager.h
+++ b/sync/internal_api/public/sync_manager.h
@@ -20,6 +20,7 @@
 #include "sync/internal_api/public/configure_reason.h"
 #include "sync/internal_api/public/engine/model_safe_worker.h"
 #include "sync/internal_api/public/engine/sync_status.h"
+#include "sync/internal_api/public/events/protocol_event.h"
 #include "sync/internal_api/public/sync_encryption_handler.h"
 #include "sync/internal_api/public/util/report_unrecoverable_error_function.h"
 #include "sync/internal_api/public/util/unrecoverable_error_handler.h"
@@ -43,6 +44,7 @@ class InternalComponentsFactory;
 class JsBackend;
 class JsEventHandler;
 class SyncEncryptionHandler;
+class ProtocolEvent;
 class SyncScheduler;
 struct UserShare;
 class CancelationSignal;
@@ -196,6 +198,8 @@ class SYNC_EXPORT SyncManager : public syncer::InvalidationHandler {
 
     virtual void OnMigrationRequested(ModelTypeSet types) = 0;
 
+    virtual void OnProtocolEvent(const ProtocolEvent& event) = 0;
+
    protected:
     virtual ~Observer();
   };
diff --git a/sync/internal_api/sync_manager_impl.cc b/sync/internal_api/sync_manager_impl.cc
index 501f8873df13eb..8ecb29fd822685 100644
--- a/sync/internal_api/sync_manager_impl.cc
+++ b/sync/internal_api/sync_manager_impl.cc
@@ -899,7 +899,6 @@ void SyncManagerImpl::RequestNudgeForDataTypes(
   base::TimeDelta nudge_delay = NudgeStrategy::GetNudgeDelayTimeDelta(
       types.First().Get(),
       this);
-  allstatus_.IncrementNudgeCounter(NUDGE_SOURCE_LOCAL);
   scheduler_->ScheduleLocalNudge(nudge_delay,
                                  types,
                                  nudge_location);
@@ -943,6 +942,11 @@ void SyncManagerImpl::OnMigrationRequested(ModelTypeSet types) {
       OnMigrationRequested(types));
 }
 
+void SyncManagerImpl::OnProtocolEvent(const ProtocolEvent& event) {
+  FOR_EACH_OBSERVER(SyncManager::Observer, observers_,
+                    OnProtocolEvent(event));
+}
+
 void SyncManagerImpl::SetJsEventHandler(
     const WeakHandle<JsEventHandler>& event_handler) {
   js_sync_manager_observer_.SetJsEventHandler(event_handler);
@@ -1029,11 +1033,9 @@ void SyncManagerImpl::OnIncomingInvalidation(
   if (invalidation_map.Empty()) {
     LOG(WARNING) << "Sync received invalidation without any type information.";
   } else {
-    allstatus_.IncrementNudgeCounter(NUDGE_SOURCE_NOTIFICATION);
     scheduler_->ScheduleInvalidationNudge(
         TimeDelta::FromMilliseconds(kSyncSchedulerDelayMsec),
         invalidation_map, FROM_HERE);
-    allstatus_.IncrementNotificationsReceived();
     debug_info_event_listener_.OnIncomingNotification(invalidation_map);
   }
 }
@@ -1045,7 +1047,6 @@ void SyncManagerImpl::RefreshTypes(ModelTypeSet types) {
   if (types.Empty()) {
     LOG(WARNING) << "Sync received refresh request with no types specified.";
   } else {
-    allstatus_.IncrementNudgeCounter(NUDGE_SOURCE_LOCAL_REFRESH);
     scheduler_->ScheduleLocalRefreshRequest(
         TimeDelta::FromMilliseconds(kSyncRefreshDelayMsec),
         types, FROM_HERE);
diff --git a/sync/internal_api/sync_manager_impl.h b/sync/internal_api/sync_manager_impl.h
index e2b3fb4f1a2f46..71890268150dad 100644
--- a/sync/internal_api/sync_manager_impl.h
+++ b/sync/internal_api/sync_manager_impl.h
@@ -142,6 +142,7 @@ class SYNC_EXPORT_PRIVATE SyncManagerImpl :
   virtual void OnRetryTimeChanged(base::Time retry_time) OVERRIDE;
   virtual void OnThrottledTypesChanged(ModelTypeSet throttled_types) OVERRIDE;
   virtual void OnMigrationRequested(ModelTypeSet types) OVERRIDE;
+  virtual void OnProtocolEvent(const ProtocolEvent& event) OVERRIDE;
 
   // ServerConnectionEventListener implementation.
   virtual void OnServerConnectionEvent(
diff --git a/sync/internal_api/sync_manager_impl_unittest.cc b/sync/internal_api/sync_manager_impl_unittest.cc
index 064db9e2be2491..7da7070223e922 100644
--- a/sync/internal_api/sync_manager_impl_unittest.cc
+++ b/sync/internal_api/sync_manager_impl_unittest.cc
@@ -29,6 +29,7 @@
 #include "sync/internal_api/public/change_record.h"
 #include "sync/internal_api/public/engine/model_safe_worker.h"
 #include "sync/internal_api/public/engine/polling_constants.h"
+#include "sync/internal_api/public/events/protocol_event.h"
 #include "sync/internal_api/public/http_post_provider_factory.h"
 #include "sync/internal_api/public/http_post_provider_interface.h"
 #include "sync/internal_api/public/read_node.h"
@@ -646,10 +647,9 @@ class SyncManagerObserverMock : public SyncManager::Observer {
                     syncer::ModelTypeSet));  // NOLINT
   MOCK_METHOD1(OnConnectionStatusChange, void(ConnectionStatus));  // NOLINT
   MOCK_METHOD1(OnUpdatedToken, void(const std::string&));  // NOLINT
-  MOCK_METHOD1(OnActionableError,
-               void(const SyncProtocolError&));  // NOLINT
-  MOCK_METHOD1(OnMigrationRequested,
-               void(syncer::ModelTypeSet));  // NOLINT
+  MOCK_METHOD1(OnActionableError, void(const SyncProtocolError&));  // NOLINT
+  MOCK_METHOD1(OnMigrationRequested, void(syncer::ModelTypeSet));  // NOLINT
+  MOCK_METHOD1(OnProtocolEvent, void(const ProtocolEvent&));  // NOLINT
 };
 
 class SyncEncryptionHandlerObserverMock
diff --git a/sync/sessions/sync_session.cc b/sync/sessions/sync_session.cc
index 957cfbfd741a15..e352e70b48eef1 100644
--- a/sync/sessions/sync_session.cc
+++ b/sync/sessions/sync_session.cc
@@ -89,5 +89,11 @@ void SyncSession::SendEventNotification(SyncCycleEvent::EventCause cause) {
                     OnSyncCycleEvent(event));
 }
 
+void SyncSession::SendProtocolEvent(const ProtocolEvent& event) {
+  FOR_EACH_OBSERVER(SyncEngineEventListener,
+                    *(context_->listeners()),
+                    OnProtocolEvent(event));
+}
+
 }  // namespace sessions
 }  // namespace syncer
diff --git a/sync/sessions/sync_session.h b/sync/sessions/sync_session.h
index 2a96fbc475e691..d61a7920f08265 100644
--- a/sync/sessions/sync_session.h
+++ b/sync/sessions/sync_session.h
@@ -30,6 +30,7 @@
 
 namespace syncer {
 class ModelSafeWorker;
+class ProtocolEvent;
 
 namespace sessions {
 
@@ -110,6 +111,8 @@ class SYNC_EXPORT_PRIVATE SyncSession {
       sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source);
   void SendEventNotification(SyncCycleEvent::EventCause cause);
 
+  void SendProtocolEvent(const ProtocolEvent& event);
+
   // TODO(akalin): Split this into context() and mutable_context().
   SyncSessionContext* context() const { return context_; }
   Delegate* delegate() const { return delegate_; }
diff --git a/sync/sync_internal_api.gypi b/sync/sync_internal_api.gypi
index 77416eb7ebe043..8f4644285924a8 100644
--- a/sync/sync_internal_api.gypi
+++ b/sync/sync_internal_api.gypi
@@ -25,17 +25,11 @@
     'internal_api/debug_info_event_listener.h',
     'internal_api/delete_journal.cc',
     'internal_api/events/commit_request_event.cc',
-    'internal_api/events/commit_request_event.h',
     'internal_api/events/commit_response_event.cc',
-    'internal_api/events/commit_response_event.h',
     'internal_api/events/configure_get_updates_request_event.cc',
-    'internal_api/events/configure_get_updates_request_event.h',
     'internal_api/events/get_updates_response_event.cc',
-    'internal_api/events/get_updates_response_event.h',
     'internal_api/events/normal_get_updates_request_event.cc',
-    'internal_api/events/normal_get_updates_request_event.h',
     'internal_api/events/poll_get_updates_request_event.cc',
-    'internal_api/events/poll_get_updates_request_event.h',
     'internal_api/events/protocol_event.cc',
     'internal_api/http_bridge.cc',
     'internal_api/http_bridge_network_resources.cc',
@@ -81,6 +75,12 @@
     'internal_api/public/engine/polling_constants.h',
     'internal_api/public/engine/sync_status.cc',
     'internal_api/public/engine/sync_status.h',
+    'internal_api/public/events/commit_request_event.h',
+    'internal_api/public/events/commit_response_event.h',
+    'internal_api/public/events/configure_get_updates_request_event.h',
+    'internal_api/public/events/get_updates_response_event.h',
+    'internal_api/public/events/normal_get_updates_request_event.h',
+    'internal_api/public/events/poll_get_updates_request_event.h',
     'internal_api/public/events/protocol_event.h',
     'internal_api/public/http_bridge.h',
     'internal_api/public/http_bridge_network_resources.h',