cc: Make most of cc::OutputSurface abstract.

content/browser/compositor/browser_compositor_output_surface.cc

Index: content/browser/compositor/browser_compositor_output_surface.cc
diff --git a/content/browser/compositor/browser_compositor_output_surface.cc b/content/browser/compositor/browser_compositor_output_surface.cc
index 3d3b6a2025c3eb11650ef0ae3836126f09efd1d5..2a017bf77bd8ec25654c19441182005ede57aa7f 100644
--- a/content/browser/compositor/browser_compositor_output_surface.cc
+++ b/content/browser/compositor/browser_compositor_output_surface.cc
@@ -60,7 +60,8 @@ BrowserCompositorOutputSurface::~BrowserCompositorOutputSurface() {
 void BrowserCompositorOutputSurface::OnUpdateVSyncParametersFromGpu(
     base::TimeTicks timebase,
     base::TimeDelta interval) {
-  DCHECK(HasClient());
+  DCHECK(client_);  // BindToClient should have been called already.
+
   if (interval.is_zero()) {
     // TODO(brianderson): We should not be receiving 0 intervals.
     interval = cc::BeginFrameArgs::DefaultInterval();
@@ -88,4 +89,10 @@ BrowserCompositorOutputSurface::GetOverlayCandidateValidator() const {
   return overlay_candidate_validator_.get();
 }
 
+bool BrowserCompositorOutputSurface::HasExternalStencilTest() const {
+  return false;
+}
+
+void BrowserCompositorOutputSurface::ApplyExternalStencil() {}
+
 }  // namespace content