Enable ScopedObservation for RenderWidgetHost::InputEventObserver

Provide a specialization for base::ScopedObservation, since the
add / remove methods for InputEventObserver are not named in the
way that ScopedObservation expects.

Bug: 1480496, 1472386
Change-Id: Ifa614f34ad94ced84588799dc46818e58d12b29c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4953774
Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1214582}

content/browser/renderer_host/render_widget_host_impl.h

@@ -992,6 +992,8 @@ class CONTENT_EXPORT RenderWidgetHostImpl
                            ShorterDelayInputEventAckTimeout);
   FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostTest,
                            AddAndRemoveInputEventObserver);
+  FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostTest,
+                           ScopedObservationWithInputEventObserver);
   FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostTest,
                            AddAndRemoveImeInputEventObserver);
   FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostTest,

content/browser/renderer_host/render_widget_host_unittest.cc

@@ -2351,6 +2351,37 @@ TEST_F(RenderWidgetHostTest, AddAndRemoveInputEventObserver) {
                                            &event_latency_metadata);
 }
 
+TEST_F(RenderWidgetHostTest, ScopedObservationWithInputEventObserver) {
+  // Verify that the specialization of `ScopedObserverationTraits` correctly
+  // adds and removes InputEventObservers.
+  MockInputEventObserver observer;
+  base::ScopedObservation<RenderWidgetHost,
+                          RenderWidgetHost::InputEventObserver>
+      scoped_observation(&observer);
+
+  // Add InputEventObserver.
+  scoped_observation.Observe(host_.get());
+
+  // Confirm OnInputEvent is triggered.
+  NativeWebKeyboardEvent native_event(WebInputEvent::Type::kChar, 0,
+                                      GetNextSimulatedEventTime());
+  ui::LatencyInfo latency_info = ui::LatencyInfo();
+  ui::EventLatencyMetadata event_latency_metadata;
+  EXPECT_CALL(observer, OnInputEvent(_)).Times(1);
+  host_->DispatchInputEventWithLatencyInfo(native_event, &latency_info,
+                                           &event_latency_metadata);
+
+  // Remove InputEventObserver.
+  scoped_observation.Reset();
+
+  // Confirm InputEventObserver is removed.
+  EXPECT_CALL(observer, OnInputEvent(_)).Times(0);
+  latency_info = ui::LatencyInfo();
+  event_latency_metadata = ui::EventLatencyMetadata();
+  host_->DispatchInputEventWithLatencyInfo(native_event, &latency_info,
+                                           &event_latency_metadata);
+}
+
 #if BUILDFLAG(IS_ANDROID)
 TEST_F(RenderWidgetHostTest, AddAndRemoveImeInputEventObserver) {
   MockInputEventObserver observer;

content/public/browser/render_widget_host.h

@@ -12,6 +12,7 @@
 
 #include "base/functional/callback.h"
 #include "base/i18n/rtl.h"
+#include "base/scoped_observation_traits.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "content/public/common/drop_data.h"
@@ -344,4 +345,21 @@ class CONTENT_EXPORT RenderWidgetHost {
 
 }  // namespace content
 
+namespace base {
+template <>
+struct ScopedObservationTraits<content::RenderWidgetHost,
+                               content::RenderWidgetHost::InputEventObserver> {
+  static void AddObserver(
+      content::RenderWidgetHost* rwh,
+      content::RenderWidgetHost::InputEventObserver* observer) {
+    rwh->AddInputEventObserver(observer);
+  }
+  static void RemoveObserver(
+      content::RenderWidgetHost* rwh,
+      content::RenderWidgetHost::InputEventObserver* observer) {
+    rwh->RemoveInputEventObserver(observer);
+  }
+};
+}  // namespace base
+
 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_H_