Don't test kEnableThreadedCompositing in WebGraphicsContext3DCommandBufferImpl

content/renderer/render_widget.cc

 // Copyright (c) 2012 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/render_widget.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ skipping 2797 matching lines @@
       static_cast<size_t>(2 * kMillisecondsPerFrame * max_mb_uploaded_per_ms);
   static const size_t kBytesPerMegabyte = 1024 * 1024;
   // We keep the MappedMemoryReclaimLimit the same as the upload limit
   // to avoid unnecessarily stalling the compositor thread.
   limits.mapped_memory_reclaim_limit =
       max_transfer_buffer_usage_mb * kBytesPerMegabyte;
 #endif
 
   base::WeakPtr<WebGraphicsContext3DSwapBuffersClient> swap_client;
 
-  if (!is_threaded_compositing_enabled_)
+  bool use_echo_for_swap_ack = true;
+  if (!is_threaded_compositing_enabled_) {
     swap_client = weak_ptr_factory_.GetWeakPtr();
+#if (defined(OS_MACOSX) || defined(OS_WIN)) && !defined(USE_AURA)
+    // ViewMsg_SwapBuffers_ACK is used instead for single-threaded path.
+    use_echo_for_swap_ack = false;
+#endif
+  }
 
   scoped_ptr<WebGraphicsContext3DCommandBufferImpl> context(
       new WebGraphicsContext3DCommandBufferImpl(
           surface_id(),
           GetURLForGraphicsContext3D(),
           gpu_channel_host.get(),
           swap_client,
+          use_echo_for_swap_ack,
           attributes,
           false /* bind generates resources */,
           limits));
   return context.Pass();
 }
 
 }  // namespace content