Make EstablishGpuChannel synchronous. Remove obsolete Synchronize msg.

content/common/gpu/gpu_channel_manager.cc

Index: content/common/gpu/gpu_channel_manager.cc
diff --git a/content/common/gpu/gpu_channel_manager.cc b/content/common/gpu/gpu_channel_manager.cc
index 849e4567b9e308bf2a21431a15eb1a2a8a6156f5..ca02d43897bea1b29b284176f4a23e91bb62a88f 100644
--- a/content/common/gpu/gpu_channel_manager.cc
+++ b/content/common/gpu/gpu_channel_manager.cc
@@ -47,7 +47,6 @@ bool GpuChannelManager::OnMessageReceived(const IPC::Message& msg) {
     IPC_MESSAGE_HANDLER(GpuMsg_CloseChannel, OnCloseChannel)
     IPC_MESSAGE_HANDLER(GpuMsg_CreateViewCommandBuffer,
                         OnCreateViewCommandBuffer)
-    IPC_MESSAGE_HANDLER(GpuMsg_Synchronize, OnSynchronize)
     IPC_MESSAGE_HANDLER(GpuMsg_VisibilityChanged, OnVisibilityChanged)
 #if defined(TOOLKIT_USES_GTK) && !defined(TOUCH_UI) || defined(OS_WIN)
     IPC_MESSAGE_HANDLER(GpuMsg_ResizeViewACK, OnResizeViewACK);
@@ -108,10 +107,6 @@ void GpuChannelManager::OnCloseChannel(
   }
 }
 
-void GpuChannelManager::OnSynchronize() {
-  Send(new GpuHostMsg_SynchronizeReply());
-}
-
 void GpuChannelManager::OnVisibilityChanged(
     int32 render_view_id, int32 renderer_id, bool visible) {
   // TODO(amarinichev): this will be used for context eviction