cc: Route offscreen context creation for compositor to the browser.

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 3b46189325efedce6a9072a133d9254f8dc1019a..1f263e200f9b1ed6da7c5cfcfd7ba8b9ce2baf49 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -22,6 +22,7 @@
 class SkBitmap;
 
 namespace cc {
+class ContextProvider;
 class Layer;
 class LayerTreeHost;
 }
@@ -69,6 +70,11 @@ class COMPOSITOR_EXPORT ContextFactory {
   // with all compositors.
   virtual WebKit::WebGraphicsContext3D* CreateOffscreenContext() = 0;
 
+  virtual scoped_refptr<cc::ContextProvider>
+      OffscreenContextProviderForMainThread() = 0;
+  virtual scoped_refptr<cc::ContextProvider>
+      OffscreenContextProviderForCompositorThread() = 0;
+
   // Destroys per-compositor data.
   virtual void RemoveCompositor(Compositor* compositor) = 0;
 };
@@ -83,6 +89,10 @@ class COMPOSITOR_EXPORT DefaultContextFactory : public ContextFactory {
   virtual cc::OutputSurface* CreateOutputSurface(
       Compositor* compositor) OVERRIDE;
   virtual WebKit::WebGraphicsContext3D* CreateOffscreenContext() OVERRIDE;
+  virtual scoped_refptr<cc::ContextProvider>
+      OffscreenContextProviderForMainThread() OVERRIDE;
+  virtual scoped_refptr<cc::ContextProvider>
+      OffscreenContextProviderForCompositorThread() OVERRIDE;
   virtual void RemoveCompositor(Compositor* compositor) OVERRIDE;
 
   bool Initialize();
@@ -97,6 +107,9 @@ class COMPOSITOR_EXPORT DefaultContextFactory : public ContextFactory {
       bool offscreen);
 
   scoped_refptr<gfx::GLShareGroup> share_group_;
+  class DefaultContextProvider;
+  scoped_refptr<DefaultContextProvider> offscreen_contexts_main_thread_;
+  scoped_refptr<DefaultContextProvider> offscreen_contexts_compositor_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultContextFactory);
 };
@@ -273,7 +286,10 @@ class COMPOSITOR_EXPORT Compositor
   virtual void didCommitAndDrawFrame() OVERRIDE;
   virtual void didCompleteSwapBuffers() OVERRIDE;
   virtual void scheduleComposite() OVERRIDE;
-
+  virtual scoped_refptr<cc::ContextProvider>
+      OffscreenContextProviderForMainThread() OVERRIDE;
+  virtual scoped_refptr<cc::ContextProvider>
+      OffscreenContextProviderForCompositorThread() OVERRIDE;
 
   int last_started_frame() { return last_started_frame_; }
   int last_ended_frame() { return last_ended_frame_; }