Make CommandBuffer::Flush asynchronous, and add CommandBuffer::FlushSync with former semantics.

chrome/renderer/command_buffer_proxy.cc

Index: chrome/renderer/command_buffer_proxy.cc
diff --git a/chrome/renderer/command_buffer_proxy.cc b/chrome/renderer/command_buffer_proxy.cc
index 21eee90e07cc66b75bb8263b19dfe0414eaaa4f2..31120316130bf8fd1762c55b0cb42239c4e00d58 100644
--- a/chrome/renderer/command_buffer_proxy.cc
+++ b/chrome/renderer/command_buffer_proxy.cc
@@ -94,7 +94,11 @@ gpu::CommandBuffer::State CommandBufferProxy::GetState() {
   return last_state_;
 }
 
-gpu::CommandBuffer::State CommandBufferProxy::Flush(int32 put_offset) {
+void CommandBufferProxy::Flush(int32 put_offset) {
+  AsyncFlush(put_offset, NULL);
+}
+
+gpu::CommandBuffer::State CommandBufferProxy::FlushSync(int32 put_offset) {
   // Send will flag state with lost context if IPC fails.
   if (last_state_.error == gpu::error::kNoError) {
     Send(new GpuCommandBufferMsg_Flush(route_id_,