services/ui: Inject GpuService instance where needed, instead of singleton.

services/ui/public/cpp/context_provider.h

 // 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.
 
 #ifndef SERVICES_UI_PUBLIC_CPP_CONTEXT_PROVIDER_H_
 #define SERVICES_UI_PUBLIC_CPP_CONTEXT_PROVIDER_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/macros.h"
 #include "cc/output/context_provider.h"
 #include "mojo/public/cpp/system/core.h"
 #include "services/ui/public/interfaces/command_buffer.mojom.h"
 
 namespace shell {
 class Connector;
 }
 
 namespace ui {
 
 class GLES2Context;
+class GpuService;
 
 class ContextProvider : public cc::ContextProvider {
  public:
-  ContextProvider();
+  explicit ContextProvider(GpuService* gpu_service);
 
   // cc::ContextProvider implementation.
   bool BindToCurrentThread() override;
   gpu::gles2::GLES2Interface* ContextGL() override;
   gpu::ContextSupport* ContextSupport() override;
   class GrContext* GrContext() override;
   void InvalidateGrContext(uint32_t state) override;
   base::Lock* GetLock() override;
   gpu::Capabilities ContextCapabilities() override;
   void DeleteCachedResources() override {}
   void SetLostContextCallback(
       const LostContextCallback& lost_context_callback) override {}
 
  protected:
   friend class base::RefCountedThreadSafe<ContextProvider>;
   ~ContextProvider() override;
 
  private:
   std::unique_ptr<GLES2Context> context_;
+  GpuService* gpu_service_;
 
   DISALLOW_COPY_AND_ASSIGN(ContextProvider);
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_CONTEXT_PROVIDER_H_