Move context-related callbacks into OutputSurface

cc/output/output_surface.h

Index: cc/output/output_surface.h
diff --git a/cc/output/output_surface.h b/cc/output/output_surface.h
index ce425eda0c61712edc6510f484467d7bea58e75a..b3e990546aba839250b51ce2213c3d6ea96a7718 100644
--- a/cc/output/output_surface.h
+++ b/cc/output/output_surface.h
@@ -22,6 +22,7 @@ namespace cc {
 
 class CompositorFrame;
 class OutputSurfaceClient;
+class OutputSurfaceCallbacks;
 
 // Represents the output surface for a compositor. The compositor owns
 // and manages its destruction. Its lifetime is:
@@ -98,6 +99,8 @@ class CC_EXPORT OutputSurface {
   scoped_ptr<cc::SoftwareOutputDevice> software_device_;
   bool has_gl_discard_backbuffer_;
 
+  scoped_ptr<OutputSurfaceCallbacks> callbacks_;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(OutputSurface);
 };