Makes BitmapUploader handle null GLES2Context

components/bitmap_uploader/bitmap_uploader.h

 // Copyright 2015 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 COMPONENTS_BITMAP_UPLOADER_BITMAP_UPLOADER_H_
 #define COMPONENTS_BITMAP_UPLOADER_BITMAP_UPLOADER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 55 matching lines @@
 
   void SetIdNamespace(uint32_t id_namespace);
 
   // WindowSurfaceClient implementation.
   void OnResourcesReturned(
       mus::WindowSurface* surface,
       mojo::Array<cc::ReturnedResource> resources) override;
 
   mus::Window* window_;
   std::unique_ptr<mus::WindowSurface> surface_;
+  // This may be null if there is an error contacting mus/initializing. We
+  // assume we'll be shutting down soon and do nothing in this case.
   std::unique_ptr<mus::GLES2Context> gles2_context_;
 
   uint32_t color_;
   int width_;
   int height_;
   Format format_;
   std::unique_ptr<std::vector<unsigned char>> bitmap_;
   uint32_t next_resource_id_;
   uint32_t id_namespace_;
   base::hash_map<uint32_t, uint32_t> resource_to_texture_id_map_;
 
   DISALLOW_COPY_AND_ASSIGN(BitmapUploader);
 };
 
 }  // namespace bitmap_uploader
 
 #endif  // COMPONENTS_BITMAP_UPLOADER_BITMAP_UPLAODER_H_