content: Allow software compositing on Chrome OS if requested

content/browser/compositor/gpu_process_transport_factory.cc

 // Copyright 2014 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/browser/compositor/gpu_process_transport_factory.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 161 matching lines @@
     return scoped_ptr<BrowserCompositorOverlayCandidateValidator>(
         new BrowserCompositorOverlayCandidateValidatorOzone(
             widget, overlay_candidates.Pass()));
   }
 #endif
   return scoped_ptr<BrowserCompositorOverlayCandidateValidator>();
 }
 
 static bool ShouldCreateGpuOutputSurface(ui::Compositor* compositor) {
 #if defined(OS_CHROMEOS)
   // Software fallback does not happen on Chrome OS.

[danakj, 2015/07/01 18:34:02]

I think you want to change here instead. There's no need to try GL a bunch of
times and fallback.

   return true;
 #endif
 
 #if defined(OS_WIN)
   if (::GetProp(compositor->widget(), kForceSoftwareCompositor) &&
       ::RemoveProp(compositor->widget(), kForceSoftwareCompositor))
     return false;
 #endif
 
   return GpuDataManagerImpl::GetInstance()->CanUseGpuBrowserCompositor();
@@ skipping 53 matching lines @@
     base::WeakPtr<ui::Compositor> compositor,
     bool create_gpu_output_surface,
     int num_attempts) {
   if (!compositor)
     return;
   PerCompositorData* data = per_compositor_data_[compositor.get()];
   DCHECK(data);
 
   if (num_attempts > kNumRetriesBeforeSoftwareFallback) {
 #if defined(OS_CHROMEOS)
-    LOG(FATAL) << "Unable to create a UI graphics context, and cannot use "
-               << "software compositing on ChromeOS.";
+    if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+            switches::kDisableGpu)) {
+      LOG(FATAL) << "Unable to create a UI graphics context, and cannot use "
+                 << "software compositing on ChromeOS.";
+    }
 #endif
     create_gpu_output_surface = false;
   }
 
   scoped_refptr<ContextProviderCommandBuffer> context_provider;
   if (create_gpu_output_surface) {
     scoped_refptr<GpuChannelHost> gpu_channel_host =
         BrowserGpuChannelHostFactory::instance()->GetGpuChannel();
     if (gpu_channel_host.get()) {
       context_provider = ContextProviderCommandBuffer::Create(
@@ skipping 347 matching lines @@
   FOR_EACH_OBSERVER(ImageTransportFactoryObserver,
                     observer_list_,
                     OnLostResources());
 
   // Kill things that use the shared context before killing the shared context.
   lost_gl_helper.reset();
   lost_shared_main_thread_contexts  = NULL;
 }
 
 }  // namespace content