content: Don't keep requesting the GpuChannelHost during shutdown.

content/browser/gpu/browser_gpu_channel_host_factory.h

Index: content/browser/gpu/browser_gpu_channel_host_factory.h
diff --git a/content/browser/gpu/browser_gpu_channel_host_factory.h b/content/browser/gpu/browser_gpu_channel_host_factory.h
index 759f936a067330a8345df7b06277116e435c64e8..64d7c495b7e253ab5c503a64800e5b344f620371 100644
--- a/content/browser/gpu/browser_gpu_channel_host_factory.h
+++ b/content/browser/gpu/browser_gpu_channel_host_factory.h
@@ -44,6 +44,8 @@ class CONTENT_EXPORT BrowserGpuChannelHostFactory
   static bool CanUseForTesting();
 
   // Overridden from gpu::GpuChannelEstablishFactory:
+  // The factory will return a null GpuChannelHost in the callback during
+  // shutdown.
   void EstablishGpuChannel(
       const gpu::GpuChannelEstablishedCallback& callback) override;
   scoped_refptr<gpu::GpuChannelHost> EstablishGpuChannelSync() override;