sync compositor: Reduce begin frame sync IPC overhead

content/browser/android/synchronous_compositor_observer.h

Index: content/browser/android/synchronous_compositor_observer.h
diff --git a/content/browser/android/synchronous_compositor_observer.h b/content/browser/android/synchronous_compositor_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..864df1645be9736343bd3e066d95edf867f86073
--- /dev/null
+++ b/content/browser/android/synchronous_compositor_observer.h
@@ -0,0 +1,61 @@
+// Copyright 2016 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 CONTENT_BROWSER_ANDROID_SYNCHRONOUS_COMPOSITOR_OBSERVER_H_
+#define CONTENT_BROWSER_ANDROID_SYNCHRONOUS_COMPOSITOR_OBSERVER_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "content/public/browser/render_process_host_observer.h"
+#include "ui/android/window_android_observer.h"
+
+namespace ui {
+class WindowAndroid;
+}
+
+namespace content {
+
+class SynchronousCompositorHost;
+
+// SynchronousCompositor class that's tied to the lifetime of a
+// RenderProcessHost. Responsible for its own lifetime.
+class SynchronousCompositorObserver : public RenderProcessHostObserver,
+                                      public ui::WindowAndroidObserver {
+ public:
+  static SynchronousCompositorObserver* GetOrCreateFor(int process_id);
+
+  // RenderProcessHostObserver overrides.
+  void RenderProcessHostDestroyed(RenderProcessHost* host) override;
+
+  // WindowAndroidObserver overrides.
+  void OnCompositingDidCommit() override;
+  void OnRootWindowVisibilityChanged(bool visible) override;
+  void OnAttachCompositor() override;
+  void OnDetachCompositor() override;
+  void OnVSync(base::TimeTicks frame_time,
+               base::TimeDelta vsync_period) override;
+  void OnActivityStopped() override;
+  void OnActivityStarted() override;
+
+  void SyncStateAfterVSync(ui::WindowAndroid* window_android,
+                           SynchronousCompositorHost* compositor_host);
+
+ private:
+  explicit SynchronousCompositorObserver(int process_id);
+  ~SynchronousCompositorObserver() override;
+
+  RenderProcessHost* const render_process_host_;
+
+  // For synchronizing renderer state after a vsync.
+  ui::WindowAndroid* window_android_in_vsync_;
+  std::vector<SynchronousCompositorHost*>
+      compositor_host_pending_renderer_state_;
+
+  DISALLOW_COPY_AND_ASSIGN(SynchronousCompositorObserver);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_ANDROID_SYNCHRONOUS_COMPOSITOR_OBSERVER_H_