Make DrawingBuffer and Canvas2DLayerBridge be cc::TextureLayerClients.

content/renderer/renderer_blink_platform_impl.h

Index: content/renderer/renderer_blink_platform_impl.h
diff --git a/content/renderer/renderer_blink_platform_impl.h b/content/renderer/renderer_blink_platform_impl.h
index 6775e77d0295fe8fbc1be38ebaf543b51246aba9..0a395a6b8f17c851cbf333e230d75bfec2cdb94b 100644
--- a/content/renderer/renderer_blink_platform_impl.h
+++ b/content/renderer/renderer_blink_platform_impl.h
@@ -189,6 +189,8 @@ class CONTENT_EXPORT RendererBlinkPlatformImpl : public BlinkPlatformImpl {
       blink::Platform::GraphicsInfo* gl_info) override;
   blink::WebGraphicsContext3DProvider*
   createSharedOffscreenGraphicsContext3DProvider() override;
+  std::unique_ptr<cc::SharedBitmap> allocateSharedBitmap(
+      const blink::WebSize& size) override;
   blink::WebCompositorSupport* compositorSupport() override;
   blink::WebString convertIDNToUnicode(const blink::WebString& host) override;
   blink::InterfaceProvider* interfaceProvider() override;