cc: Make most of cc::OutputSurface abstract.

android_webview/browser/parent_output_surface.h

Index: android_webview/browser/parent_output_surface.h
diff --git a/android_webview/browser/parent_output_surface.h b/android_webview/browser/parent_output_surface.h
index 48b7853484439449297c83df45aa5616b842618e..8b5fed6668cd9ba21996498b9fd38d6178588048 100644
--- a/android_webview/browser/parent_output_surface.h
+++ b/android_webview/browser/parent_output_surface.h
@@ -19,6 +19,9 @@ class ParentOutputSurface : NON_EXPORTED_BASE(public cc::OutputSurface) {
 
   // OutputSurface overrides.
   void DidLoseOutputSurface() override;
+  void EnsureBackbuffer() override;
+  void DiscardBackbuffer() override;
+  void BindFramebuffer() override;
   void Reshape(const gfx::Size& size,
                float scale_factor,
                const gfx::ColorSpace& color_space,
@@ -27,6 +30,10 @@ class ParentOutputSurface : NON_EXPORTED_BASE(public cc::OutputSurface) {
   bool HasExternalStencilTest() const override;
   void ApplyExternalStencil() override;
   uint32_t GetFramebufferCopyTextureFormat() override;
+  cc::OverlayCandidateValidator* GetOverlayCandidateValidator() const override;
+  bool IsDisplayedAsOverlayPlane() const override;
+  unsigned GetOverlayTextureId() const override;
+  bool SurfaceIsSuspendForRecycle() const override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ParentOutputSurface);