Don't request a depth/stencil buffer for the compositor

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 587 matching lines @@
   // Mac OS X essentially always behaves as though it's rendering offscreen.
   // Multisampling has a heavy cost especially on devices with relatively low
   // fill rate like most notebooks, and the Mac implementation would need to
   // be optimized to resolve directly into the IOSurface shared between the
   // GPU and browser processes. For these reasons and to avoid platform
   // disparities we explicitly disable antialiasing.
   WebKit::WebGraphicsContext3D::Attributes attributes;
   attributes.antialias = false;
   attributes.shareResources = true;
   attributes.noAutomaticFlushes = true;
+  attributes.depth = false;
+  attributes.stencil = false;
   WebGraphicsContext3DCommandBufferImpl* context =
       CreateGraphicsContext3D(attributes);
   if (!context)
     return scoped_ptr<cc::OutputSurface>();
 
   bool composite_to_mailbox =
       command_line.HasSwitch(cc::switches::kCompositeToMailbox) &&
       !command_line.HasSwitch(switches::kEnableDelegatedRenderer);
   // No swap throttling yet when compositing on the main thread.
   DCHECK(!composite_to_mailbox || is_threaded_compositing_enabled_);
@@ skipping 1732 matching lines @@
 
   if (!context->Initialize(
           attributes,
           false /* bind generates resources */,
           CAUSE_FOR_GPU_LAUNCH_WEBGRAPHICSCONTEXT3DCOMMANDBUFFERIMPL_INITIALIZE))
     return NULL;
   return context.release();
 }
 
 }  // namespace content