Fixes crash in ViewManager during shutdown

The crash happens because the CommandBufferImpl can be destroyed on
another thread. This is because the CommandBufferImpl uses a
strongbinding that is created on another thread. This means if there
is a connection error the CommandBufferImpl is destroyed on the
background thread. CommandBufferImpl has references to a bunch of
things that need to be destroyed on the main thread.

BUG=none
TEST=none
R=jam@chromium.org

Review URL: https://codereview.chromium.org/1179933003

Cr-Commit-Position: refs/heads/master@{#334082}

components/view_manager/gles2/command_buffer_impl.cc

@@ -68,13 +68,6 @@ CommandBufferImpl::CommandBufferImpl(
                             base::Unretained(this), base::Passed(&request)));
 }
 
-CommandBufferImpl::~CommandBufferImpl() {
-  if (observer_)
-    observer_->OnCommandBufferImplDestroyed();
-  driver_task_runner_->PostTask(
-      FROM_HERE, base::Bind(&DestroyDriver, base::Passed(&driver_)));
-}
-
 void CommandBufferImpl::Initialize(
     mojo::CommandBufferSyncClientPtr sync_client,
     mojo::CommandBufferSyncPointClientPtr sync_point_client,
@@ -144,9 +137,24 @@ void CommandBufferImpl::Echo(const mojo::Callback<void()>& callback) {
                                         base::Bind(&RunCallback, callback));
 }
 
+CommandBufferImpl::~CommandBufferImpl() {
+  if (observer_)
+    observer_->OnCommandBufferImplDestroyed();
+  driver_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&DestroyDriver, base::Passed(&driver_)));
+}
+
 void CommandBufferImpl::BindToRequest(
     mojo::InterfaceRequest<mojo::CommandBuffer> request) {
   binding_.Bind(request.Pass());
+  binding_.set_error_handler(this);
+}
+
+void CommandBufferImpl::OnConnectionError() {
+  // OnConnectionError() is called on the background thread
+  // |control_task_runner| but objects we own (such as CommandBufferDriver)
+  // need to be destroyed on the thread we were created on.
+  driver_task_runner_->DeleteSoon(FROM_HERE, this);
 }
 
 void CommandBufferImpl::DidLoseContext() {

components/view_manager/gles2/command_buffer_impl.h

@@ -10,7 +10,7 @@
 #include "base/single_thread_task_runner.h"
 #include "components/view_manager/public/interfaces/command_buffer.mojom.h"
 #include "components/view_manager/public/interfaces/viewport_parameter_listener.mojom.h"
-#include "third_party/mojo/src/mojo/public/cpp/bindings/strong_binding.h"
+#include "third_party/mojo/src/mojo/public/cpp/bindings/binding.h"
 
 namespace gpu {
 class SyncPointManager;
@@ -24,15 +24,15 @@ class CommandBufferImplObserver;
 // so that we can insert sync points without blocking on the GL driver. It
 // forwards most method calls to the CommandBufferDriver, which runs on the
 // same thread as the native viewport.
-class CommandBufferImpl : public mojo::CommandBuffer {
+class CommandBufferImpl : public mojo::CommandBuffer,
+                          public mojo::ErrorHandler {
  public:
   CommandBufferImpl(
       mojo::InterfaceRequest<CommandBuffer> request,
       mojo::ViewportParameterListenerPtr listener,
       scoped_refptr<base::SingleThreadTaskRunner> control_task_runner,
       gpu::SyncPointManager* sync_point_manager,
       scoped_ptr<CommandBufferDriver> driver);
-  ~CommandBufferImpl() override;
 
   void Initialize(mojo::CommandBufferSyncClientPtr sync_client,
                   mojo::CommandBufferSyncPointClientPtr sync_point_client,
@@ -58,14 +58,21 @@ class CommandBufferImpl : public mojo::CommandBuffer {
   }
 
  private:
+  friend class base::DeleteHelper<CommandBufferImpl>;
+
+  ~CommandBufferImpl() override;
+
   void BindToRequest(mojo::InterfaceRequest<CommandBuffer> request);
 
+  // mojo::ErrorHandler:
+  void OnConnectionError() override;
+
   scoped_refptr<gpu::SyncPointManager> sync_point_manager_;
   scoped_refptr<base::SingleThreadTaskRunner> driver_task_runner_;
   scoped_ptr<CommandBufferDriver> driver_;
   mojo::CommandBufferSyncPointClientPtr sync_point_client_;
   mojo::ViewportParameterListenerPtr viewport_parameter_listener_;
-  mojo::StrongBinding<CommandBuffer> binding_;
+  mojo::Binding<CommandBuffer> binding_;
   CommandBufferImplObserver* observer_;
 
   base::WeakPtrFactory<CommandBufferImpl> weak_factory_;