Added a way for sync point clients to issue out of order waits.

content/common/gpu/gpu_channel.h

Index: content/common/gpu/gpu_channel.h
diff --git a/content/common/gpu/gpu_channel.h b/content/common/gpu/gpu_channel.h
index e170b21332474e37ad5caf235df92aa192da7037..319f81d40ed20163d7ee7f24b4ee5c0ad2261004 100644
--- a/content/common/gpu/gpu_channel.h
+++ b/content/common/gpu/gpu_channel.h
@@ -432,8 +432,12 @@ class GpuChannelMessageQueue
 
   GpuChannelMessage* GetNextMessage() const;
 
+  // Should be called before a message begins to be processed.
   void BeginMessageProcessing(const GpuChannelMessage* msg);
 
+  // Should be called if a message began processing but did not finish.
+  void PauseMessageProcessing(const GpuChannelMessage* msg);
+
   // Should be called after a message returned by GetNextMessage is processed.
   // Returns true if there are more messages on the queue.
   bool MessageProcessed();