content: Fix Context creation logic in ContextProviderFactoryImpl.

content/browser/gpu/browser_gpu_channel_host_factory.h

 // 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.
 
 #ifndef CONTENT_BROWSER_GPU_BROWSER_GPU_CHANNEL_HOST_FACTORY_H_
 #define CONTENT_BROWSER_GPU_BROWSER_GPU_CHANNEL_HOST_FACTORY_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 10 matching lines @@
 
 namespace content {
 class BrowserGpuMemoryBufferManager;
 
 class CONTENT_EXPORT BrowserGpuChannelHostFactory
     : public gpu::GpuChannelHostFactory,
       public gpu::GpuChannelEstablishFactory {
  public:
   static void Initialize(bool establish_gpu_channel);
   static void Terminate();
+
+  // The instance can be null during shutdown.
   static BrowserGpuChannelHostFactory* instance() { return instance_; }
 
   // Overridden from gpu::GpuChannelHostFactory:
   bool IsMainThread() override;
   scoped_refptr<base::SingleThreadTaskRunner> GetIOThreadTaskRunner() override;
   std::unique_ptr<base::SharedMemory> AllocateSharedMemory(
       size_t size) override;
 
   int GpuProcessHostId() { return gpu_host_id_; }
   gpu::GpuChannelHost* GetGpuChannel();
@@ skipping 33 matching lines @@
   std::vector<gpu::GpuChannelEstablishedCallback> established_callbacks_;
 
   static BrowserGpuChannelHostFactory* instance_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserGpuChannelHostFactory);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_GPU_BROWSER_GPU_CHANNEL_HOST_FACTORY_H_