cc: Make most of cc::OutputSurface abstract.

android_webview/browser/parent_output_surface.cc

Index: android_webview/browser/parent_output_surface.cc
diff --git a/android_webview/browser/parent_output_surface.cc b/android_webview/browser/parent_output_surface.cc
index 1de4b3fa840b029d065ac653d66e9d31b1d3375b..ee88fa1356abb3fc14d35603aa1fa1e2883f20d8 100644
--- a/android_webview/browser/parent_output_surface.cc
+++ b/android_webview/browser/parent_output_surface.cc
@@ -25,6 +25,16 @@ void ParentOutputSurface::DidLoseOutputSurface() {
   LOG(FATAL) << "Render thread context loss";
 }
 
+void ParentOutputSurface::EnsureBackbuffer() {}
+
+void ParentOutputSurface::DiscardBackbuffer() {
+  context_provider()->ContextGL()->DiscardBackbufferCHROMIUM();
+}
+
+void ParentOutputSurface::BindFramebuffer() {
+  context_provider()->ContextGL()->BindFramebuffer(GL_FRAMEBUFFER, 0);
+}
+
 void ParentOutputSurface::Reshape(const gfx::Size& size,
                                   float scale_factor,
                                   const gfx::ColorSpace& color_space,
@@ -69,4 +79,21 @@ uint32_t ParentOutputSurface::GetFramebufferCopyTextureFormat() {
   return gl->GetCopyTextureInternalFormat();
 }
 
+cc::OverlayCandidateValidator*
+ParentOutputSurface::GetOverlayCandidateValidator() const {
+  return nullptr;
+}
+
+bool ParentOutputSurface::IsDisplayedAsOverlayPlane() const {
+  return false;
+}
+
+unsigned ParentOutputSurface::GetOverlayTextureId() const {
+  return 0;
+}
+
+bool ParentOutputSurface::SurfaceIsSuspendForRecycle() const {
+  return false;
+}
+
 }  // namespace android_webview