mus: Always use the GPU compositor for mus.

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 <utility>
 
 #include "base/bind.h"
@@ skipping 250 matching lines @@
 #endif
 
   return validator;
 }
 
 static bool ShouldCreateGpuOutputSurface(ui::Compositor* compositor) {
 #if defined(OS_CHROMEOS)
   // Software fallback does not happen on Chrome OS.
   return true;
 #endif
+  if (IsUsingMus())
+    return true;
 
 #if defined(OS_WIN)
   if (::GetProp(compositor->widget(), kForceSoftwareCompositor) &&
       ::RemoveProp(compositor->widget(), kForceSoftwareCompositor))
     return false;
 #endif
 
   return GpuDataManagerImpl::GetInstance()->CanUseGpuBrowserCompositor();
 }
 
@@ skipping 41 matching lines @@
   // The widget might have been released in the meantime.
   PerCompositorDataMap::iterator it =
       per_compositor_data_.find(compositor.get());
   if (it == per_compositor_data_.end())
     return;
 
   PerCompositorData* data = it->second;
   DCHECK(data);
 
   if (num_attempts > kNumRetriesBeforeSoftwareFallback) {
+    bool fatal = IsUsingMus();
 #if defined(OS_CHROMEOS)
-    LOG(FATAL) << "Unable to create a UI graphics context, and cannot use "
-               << "software compositing on ChromeOS.";
+    fatal = true;
 #endif
+    LOG_IF(FATAL, fatal) << "Unable to create a UI graphics context, and "
+                         << "cannot use software compositing on ChromeOS.";
     create_gpu_output_surface = false;
   }
 
 #if defined(OS_WIN)
   gfx::RenderingWindowManager::GetInstance()->RegisterParent(
       compositor->widget());
 #endif
 
   scoped_refptr<cc::VulkanInProcessContextProvider> vulkan_context_provider =
       SharedVulkanContextProvider();
@@ skipping 512 matching lines @@
       shared_vulkan_context_provider_ =
           cc::VulkanInProcessContextProvider::Create();
     }
 
     shared_vulkan_context_provider_initialized_ = true;
   }
   return shared_vulkan_context_provider_;
 }
 
 }  // namespace content