cc: Make most of cc::OutputSurface abstract.

cc/test/fake_output_surface.cc

Index: cc/test/fake_output_surface.cc
diff --git a/cc/test/fake_output_surface.cc b/cc/test/fake_output_surface.cc
index a7f4007b08e14744640329b6c646bfaeb6e8c41b..f124764458ae3db707558f207689985fb55c3433 100644
--- a/cc/test/fake_output_surface.cc
+++ b/cc/test/fake_output_surface.cc
@@ -55,12 +55,7 @@ void FakeOutputSurface::SwapBuffers(CompositorFrame frame) {
 }
 
 void FakeOutputSurface::BindFramebuffer() {
-  if (framebuffer_) {
-    context_provider_->ContextGL()->BindFramebuffer(GL_FRAMEBUFFER,
-                                                    framebuffer_);
-  } else {
-    OutputSurface::BindFramebuffer();
-  }
+  context_provider_->ContextGL()->BindFramebuffer(GL_FRAMEBUFFER, framebuffer_);
 }
 
 uint32_t FakeOutputSurface::GetFramebufferCopyTextureFormat() {
@@ -79,11 +74,6 @@ bool FakeOutputSurface::BindToClient(OutputSurfaceClient* client) {
   }
 }
 
-void FakeOutputSurface::DetachFromClient() {
-  ReturnResourcesHeldByParent();
-  OutputSurface::DetachFromClient();
-}
-
 bool FakeOutputSurface::HasExternalStencilTest() const {
   return has_external_stencil_test_;
 }
@@ -97,6 +87,14 @@ OverlayCandidateValidator* FakeOutputSurface::GetOverlayCandidateValidator()
   return overlay_candidate_validator_;
 }
 
+bool FakeOutputSurface::IsDisplayedAsOverlayPlane() const {
+  return false;
+}
+
+unsigned FakeOutputSurface::GetOverlayTextureId() const {
+  return 0;
+}
+
 void FakeOutputSurface::ReturnResourcesHeldByParent() {
   // Check |delegated_frame_data| because we shouldn't reclaim resources
   // for the Display which does not swap delegated frames.