Call OnSwapBuffersComplete at the end of each frame

cc/output/output_surface.cc

 // Copyright (c) 2013 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 "cc/output/output_surface.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 118 matching lines @@
 gfx::Size OutputSurface::SurfaceSize() const {
   return surface_size_;
 }
 
 void OutputSurface::BindFramebuffer() {
   DCHECK(context3d_);
   context3d_->bindFramebuffer(GL_FRAMEBUFFER, 0);
 }
 
 void OutputSurface::SwapBuffers(const ui::LatencyInfo& latency_info) {
-  DCHECK(context3d_);
-  // Note that currently this has the same effect as SwapBuffers; we should
-  // consider exposing a different entry point on WebGraphicsContext3D.
-  context3d_->prepareTexture();
+  if (context3d_) {
+    // Note that currently this has the same effect as SwapBuffers; we should
+    // consider exposing a different entry point on WebGraphicsContext3D.
+    context3d_->prepareTexture();
+  }
 }
 
 void OutputSurface::PostSubBuffer(gfx::Rect rect,
                                   const ui::LatencyInfo& latency_info) {
   DCHECK(context3d_);
   context3d_->postSubBufferCHROMIUM(
       rect.x(), rect.y(), rect.width(), rect.height());
 }
 
 }  // namespace cc