[android] Make RWHVAndroid a BeginFrameObserver.

ui/android/window_android.h

Index: ui/android/window_android.h
diff --git a/ui/android/window_android.h b/ui/android/window_android.h
index 05279ced4c92a2a9e8827b15c67e0c94187a9e11..762406aa51ef389291fb573539f7a5f31f38dabb 100644
--- a/ui/android/window_android.h
+++ b/ui/android/window_android.h
@@ -6,6 +6,7 @@
 #define UI_ANDROID_WINDOW_ANDROID_H_
 
 #include <jni.h>
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -18,9 +19,13 @@
 #include "ui/android/view_android.h"
 #include "ui/gfx/geometry/vector2d_f.h"
 
+namespace cc {
+class BeginFrameSource;
+}  // namespace cc
+
 namespace display {
 class DisplayAndroidManager;
-}
+}  // namespace display
 
 namespace ui {
 
@@ -59,8 +64,9 @@ class UI_ANDROID_EXPORT WindowAndroid : public ViewAndroid {
   void RemoveObserver(WindowAndroidObserver* observer);
 
   WindowAndroidCompositor* GetCompositor() { return compositor_; }
+  cc::BeginFrameSource* GetBeginFrameSource();
 
-  void RequestVSyncUpdate();
+  void SetNeedsBeginFrames(bool needs_begin_frames);

[boliu, 2016/12/12 21:41:48]

private, and friend WindowBeginFrameSource?

[Eric Seckler, 2016/12/13 10:03:56]

Done.

   void SetNeedsAnimate();
   void Animate(base::TimeTicks begin_frame_time);
   void OnVSync(JNIEnv* env,
@@ -88,6 +94,8 @@ class UI_ANDROID_EXPORT WindowAndroid : public ViewAndroid {
 
   ~WindowAndroid() override;
 
+  void RequestVSyncUpdate();
+
   // ViewAndroid overrides.
   WindowAndroid* GetWindowAndroid() const override;
 
@@ -101,6 +109,10 @@ class UI_ANDROID_EXPORT WindowAndroid : public ViewAndroid {
 
   base::ObserverList<WindowAndroidObserver> observer_list_;
 
+  class WindowBeginFrameSource;
+  std::unique_ptr<WindowBeginFrameSource> begin_frame_source_;
+  bool needs_begin_frames_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowAndroid);
 };