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 ad1e7d40736cb2172b58ec72e74a5b3594fa7abb..739c271ee7982d3a2620ddf10f134a0dc37a17f4 100644
--- a/android_webview/browser/parent_output_surface.h
+++ b/android_webview/browser/parent_output_surface.h
@@ -20,6 +20,9 @@ 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,
@@ -28,6 +31,10 @@ 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;
 
   void SetGLState(const ScopedAppGLStateRestore& gl_state);