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

chrome/gpu/gpu_command_buffer_stub.cc

Index: chrome/gpu/gpu_command_buffer_stub.cc
diff --git a/chrome/gpu/gpu_command_buffer_stub.cc b/chrome/gpu/gpu_command_buffer_stub.cc
index 592e04f91a97cdaab4c65ea1411969ef948b2950..5bb22f49ed27e65bfc17c86424445a50270070f1 100644
--- a/chrome/gpu/gpu_command_buffer_stub.cc
+++ b/chrome/gpu/gpu_command_buffer_stub.cc
@@ -289,11 +289,11 @@ void GpuCommandBufferStub::OnFlush(int32 put_offset,
   if (channel_->IsRenderViewGone(render_view_id_))
     processor_->DidDestroySurface();
 #endif
-  *state = command_buffer_->Flush(put_offset);
+  *state = command_buffer_->FlushSync(put_offset);
 }
 
 void GpuCommandBufferStub::OnAsyncFlush(int32 put_offset) {
-  gpu::CommandBuffer::State state = command_buffer_->Flush(put_offset);
+  gpu::CommandBuffer::State state = command_buffer_->FlushSync(put_offset);
   Send(new GpuCommandBufferMsg_UpdateState(route_id_, state));
 }