sync compositor: Reduce begin frame sync IPC overhead

content/renderer/android/synchronous_compositor_filter.cc

Index: content/renderer/android/synchronous_compositor_filter.cc
diff --git a/content/renderer/android/synchronous_compositor_filter.cc b/content/renderer/android/synchronous_compositor_filter.cc
index 44e1087cbdc376c6b13b0b4f51ef60d90c4dfb88..3dbadcc1ccb4a2787afd5dd9a19bdd5b28c13274 100644
--- a/content/renderer/android/synchronous_compositor_filter.cc
+++ b/content/renderer/android/synchronous_compositor_filter.cc
@@ -12,6 +12,7 @@
 #include "content/common/android/sync_compositor_messages.h"
 #include "content/common/input_messages.h"
 #include "content/renderer/android/synchronous_compositor_proxy.h"
+#include "ipc/ipc_message_macros.h"
 #include "ui/events/blink/synchronous_input_handler_proxy.h"
 
 namespace content {
@@ -82,6 +83,15 @@ void SynchronousCompositorFilter::OnMessageReceivedOnCompositorThread(
     return;
   }
 
+  bool handled = true;
+  IPC_BEGIN_MESSAGE_MAP(SynchronousCompositorFilter, message)
+    IPC_MESSAGE_HANDLER(SyncCompositorMsg_SynchronizeRendererState,
+                        OnSynchronizeRendererState)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+  if (handled)
+    return;
+
   if (!message.is_sync())
     return;
   IPC::Message* reply = IPC::SyncMessage::GenerateReply(&message);
@@ -142,6 +152,18 @@ void SynchronousCompositorFilter::RegisterOutputSurface(
   }
 }
 
+void SynchronousCompositorFilter::OnSynchronizeRendererState(
+    const std::vector<int>& routing_ids,
+    std::vector<SyncCompositorCommonRendererParams>* out) {
+  for (int routing_id : routing_ids) {
+    SynchronousCompositorProxy* proxy = FindProxy(routing_id);
+    SyncCompositorCommonRendererParams param;
+    if (proxy)
+      proxy->PopulateCommonParams(&param);
+    out->push_back(param);
+  }
+}
+
 void SynchronousCompositorFilter::UnregisterOutputSurface(
     int routing_id,
     SynchronousCompositorOutputSurface* output_surface) {