aura: Remove old GL paths from RenderWidgetHostViewAura.

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/debug/trace_event_synthetic_delay.h"
@@ skipping 912 matching lines @@
       !command_line.HasSwitch(switches::kDisableDelegatedRenderer)) {
     DCHECK(is_threaded_compositing_enabled_);
     return scoped_ptr<cc::OutputSurface>(
         new DelegatedCompositorOutputSurface(
             routing_id(),
             output_surface_id,
             context_provider,
             scoped_ptr<cc::SoftwareOutputDevice>()));
   }
   if (command_line.HasSwitch(cc::switches::kCompositeToMailbox)) {
-    DCHECK(is_threaded_compositing_enabled_);
+    // Composite-to-mailbox is currently used for layout tests in order to cause
+    // them to draw inside in the renderer to do the readback there. This should
+    // no longer be the case when crbug.com/311404 is fixed.
+    DCHECK(is_threaded_compositing_enabled_ ||
+           RenderThreadImpl::current()->layout_test_mode());
     cc::ResourceFormat format = cc::RGBA_8888;
 #if defined(OS_ANDROID)
     if (base::android::SysUtils::IsLowEndDevice())
       format = cc::RGB_565;
 #endif
     return scoped_ptr<cc::OutputSurface>(
         new MailboxOutputSurface(
             routing_id(),
             output_surface_id,
             context_provider,
@@ skipping 1889 matching lines @@
 
 void RenderWidget::RegisterSwappedOutChildFrame(RenderFrameImpl* frame) {
   swapped_out_frames_.AddObserver(frame);
 }
 
 void RenderWidget::UnregisterSwappedOutChildFrame(RenderFrameImpl* frame) {
   swapped_out_frames_.RemoveObserver(frame);
 }
 
 }  // namespace content