Flush during SwapBuffers only on Mac OS X in order to force results to

content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.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.
 
 #if defined(ENABLE_GPU)
 
 #include "content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h"
 
 #include "gpu/GLES2/gl2.h"
 #ifndef GL_GLEXT_PROTOTYPES
@@ skipping 217 matching lines @@
 void WebGraphicsContext3DCommandBufferImpl::prepareTexture() {
   // Copies the contents of the off-screen render target into the texture
   // used by the compositor.
 #ifndef WTF_USE_THREADED_COMPOSITING
   RenderView* renderview =
       web_view_ ? RenderView::FromWebView(web_view_) : NULL;
   if (renderview)
     renderview->OnViewContextSwapBuffersPosted();
 #endif
   context_->SwapBuffers();
+#if defined(OS_MACOSX)
+  // It appears that making the compositor's on-screen context current on
+  // other platforms implies this flush. TODO(kbr): this means that the
+  // TOUCH build and, in the future, other platforms might need this.
+  gl_->Flush();
+#endif
 }
 
 void WebGraphicsContext3DCommandBufferImpl::reshape(int width, int height) {
   cached_width_ = width;
   cached_height_ = height;
 
   gl_->ResizeCHROMIUM(width, height);
 
 #ifdef FLIP_FRAMEBUFFER_VERTICALLY
   scanline_.reset(new uint8[width * 4]);
@@ skipping 811 matching lines @@
   }
 #ifndef WTF_USE_THREADED_COMPOSITING
   RenderView* renderview =
       web_view_ ? RenderView::FromWebView(web_view_) : NULL;
   if (renderview)
     renderview->OnViewContextSwapBuffersAborted();
 #endif
 }
 
 #endif  // defined(ENABLE_GPU)