sync compositor: Implement post metadata to UI

content/browser/android/synchronous_compositor_browser_filter.h

Index: content/browser/android/synchronous_compositor_browser_filter.h
diff --git a/content/browser/android/synchronous_compositor_browser_filter.h b/content/browser/android/synchronous_compositor_browser_filter.h
index 097ff7268a6e24240e1f43f71dde13ac9f369b6f..bd40f5e053190587fdfdf6078233cc49bc486f57 100644
--- a/content/browser/android/synchronous_compositor_browser_filter.h
+++ b/content/browser/android/synchronous_compositor_browser_filter.h
@@ -11,6 +11,7 @@
 
 #include "base/macros.h"
 #include "base/synchronization/lock.h"
+#include "cc/output/compositor_frame_metadata.h"
 #include "content/public/browser/android/synchronous_compositor.h"
 #include "content/public/browser/browser_message_filter.h"
 #include "ui/android/window_android_observer.h"
@@ -47,6 +48,10 @@ class SynchronousCompositorBrowserFilter : public ui::WindowAndroidObserver,
 
   void SyncStateAfterVSync(ui::WindowAndroid* window_android,
                            SynchronousCompositorHost* compositor_host);
+
+  // Calls from SynchronousCompositorHost.
+  void RegisterHost(SynchronousCompositorHost* host);
+  void UnregisterHost(SynchronousCompositorHost* host);
   void SetFrameFuture(
       int routing_id,
       scoped_refptr<SynchronousCompositor::FrameFuture> frame_future);
@@ -55,6 +60,8 @@ class SynchronousCompositorBrowserFilter : public ui::WindowAndroidObserver,
   ~SynchronousCompositorBrowserFilter() override;
 
   bool ReceiveFrame(const IPC::Message& message);
+  void ProcessFrameMetadataOnUIThread(int routing_id,
+                                      cc::CompositorFrameMetadata metadata);
   void SignalAllFutures();
 
   RenderProcessHost* const render_process_host_;
@@ -64,6 +71,10 @@ class SynchronousCompositorBrowserFilter : public ui::WindowAndroidObserver,
   std::vector<SynchronousCompositorHost*>
       compositor_host_pending_renderer_state_;
 
+  // Only accessed on the UI thread. Note this is not a parallel map to
+  // |future_map_|.
+  std::map<int, SynchronousCompositorHost*> hosts_;
+
   base::Lock future_map_lock_;  // Protects fields below.
   bool filter_ready_ = false;
   using FrameFutureQueue =