Allow FlushSyncs to short circuit

content/renderer/gpu/command_buffer_proxy.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/gpu/command_buffer_proxy.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/process_util.h"
 #include "base/shared_memory.h"
@@ skipping 163 matching lines @@
 }
 
 gpu::CommandBuffer::State CommandBufferProxy::GetLastState() {
   return last_state_;
 }
 
 void CommandBufferProxy::Flush(int32 put_offset) {
   if (last_state_.error != gpu::error::kNoError)
     return;
 
+  TRACE_EVENT1("gpu", "CommandBufferProxy::Flush", "put_offset", put_offset);
+
   Send(new GpuCommandBufferMsg_AsyncFlush(route_id_,
                                           put_offset,
                                           ++flush_count_));
 }
 
 gpu::CommandBuffer::State CommandBufferProxy::FlushSync(int32 put_offset,
                                                         int32 last_known_get) {
-  TRACE_EVENT0("gpu", "CommandBufferProxy::FlushSync");
+  TRACE_EVENT1("gpu", "CommandBufferProxy::FlushSync", "put_offset",
+               put_offset);
+  Flush(put_offset);
   if (last_known_get == last_state_.get_offset) {
     // Send will flag state with lost context if IPC fails.
     if (last_state_.error == gpu::error::kNoError) {
       gpu::CommandBuffer::State state;
-      if (Send(new GpuCommandBufferMsg_Flush(route_id_,
-                                             put_offset,
-                                             last_known_get,
-                                             ++flush_count_,
-                                             &state)))
+      if (Send(new GpuCommandBufferMsg_GetStateFast(route_id_,
+                                                    &state)))
         OnUpdateState(state);
     }
-  } else {
-    Flush(put_offset);
   }
 
   return last_state_;
 }
 
 void CommandBufferProxy::SetGetOffset(int32 get_offset) {
   // Not implemented in proxy.
   NOTREACHED();
 }
 
@@ skipping 227 matching lines @@
   delete msg;
   return false;
 }
 
 void CommandBufferProxy::OnUpdateState(const gpu::CommandBuffer::State& state) {
   // Handle wraparound. It works as long as we don't have more than 2B state
   // updates in flight across which reordering occurs.
   if (state.generation - last_state_.generation < 0x80000000U)
     last_state_ = state;
 }