Add check for renderer client id.

content/browser/renderer_host/offscreen_canvas_provider_impl.h

 // Copyright 2016 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_RENDERER_HOST_OFFSCREEN_CANVAS_PROVIDER_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_OFFSCREEN_CANVAS_PROVIDER_IMPL_H_
 
 #include "cc/surfaces/frame_sink_id.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "third_party/WebKit/public/platform/modules/offscreencanvas/offscreen_canvas_surface.mojom.h"
 
 namespace content {
 
 // Creates OffscreenCanvasSurfaces and MojoCompositorFrameSinks for a renderer.
 class OffscreenCanvasProviderImpl
     : public blink::mojom::OffscreenCanvasProvider {
  public:
-  OffscreenCanvasProviderImpl();
+  explicit OffscreenCanvasProviderImpl(uint32_t renderer_client_id);
   ~OffscreenCanvasProviderImpl() override;
 
   void Add(blink::mojom::OffscreenCanvasProviderRequest request);
 
   // blink::mojom::OffscreenCanvasProvider implementation.
   void CreateOffscreenCanvasSurface(
       const cc::FrameSinkId& parent_frame_sink_id,
       const cc::FrameSinkId& frame_sink_id,
       cc::mojom::FrameSinkManagerClientPtr client,
       blink::mojom::OffscreenCanvasSurfaceRequest request) override;
   void CreateCompositorFrameSink(
       const cc::FrameSinkId& frame_sink_id,
       cc::mojom::MojoCompositorFrameSinkClientPtr client,
       cc::mojom::MojoCompositorFrameSinkRequest request) override;
 
  private:
+  // FrameSinkIds for offscreen canvas must use the renderer client id.
+  const uint32_t renderer_client_id_;
+
   mojo::BindingSet<blink::mojom::OffscreenCanvasProvider> bindings_;
 
   DISALLOW_COPY_AND_ASSIGN(OffscreenCanvasProviderImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_OFFSCREEN_CANVAS_PROVIDER_IMPL_H_