cc: Make most of cc::OutputSurface abstract.

content/browser/compositor/software_browser_compositor_output_surface.cc

Index: content/browser/compositor/software_browser_compositor_output_surface.cc
diff --git a/content/browser/compositor/software_browser_compositor_output_surface.cc b/content/browser/compositor/software_browser_compositor_output_surface.cc
index 2ef0c42ec5855c4e5b7469e7c11de1568fbef3f1..f23c6fc755603cc6b37d36626d30df90cc7b9bcd 100644
--- a/content/browser/compositor/software_browser_compositor_output_surface.cc
+++ b/content/browser/compositor/software_browser_compositor_output_surface.cc
@@ -33,6 +33,19 @@ SoftwareBrowserCompositorOutputSurface::
     ~SoftwareBrowserCompositorOutputSurface() {
 }
 
+void SoftwareBrowserCompositorOutputSurface::EnsureBackbuffer() {
+  software_device()->EnsureBackbuffer();
+}
+
+void SoftwareBrowserCompositorOutputSurface::DiscardBackbuffer() {
+  software_device()->DiscardBackbuffer();
+}
+
+void SoftwareBrowserCompositorOutputSurface::BindFramebuffer() {
+  // Not used for software surfaces.
+  NOTREACHED();
+}
+
 void SoftwareBrowserCompositorOutputSurface::SwapBuffers(
     cc::CompositorFrame frame) {
   base::TimeTicks swap_time = base::TimeTicks::Now();
@@ -56,9 +69,17 @@ void SoftwareBrowserCompositorOutputSurface::SwapBuffers(
   PostSwapBuffersComplete();
 }
 
-void SoftwareBrowserCompositorOutputSurface::BindFramebuffer() {
-  // Not used for software surfaces.
-  NOTREACHED();
+bool SoftwareBrowserCompositorOutputSurface::IsDisplayedAsOverlayPlane() const {
+  return false;
+}
+
+unsigned SoftwareBrowserCompositorOutputSurface::GetOverlayTextureId() const {
+  return 0;
+}
+
+bool SoftwareBrowserCompositorOutputSurface::SurfaceIsSuspendForRecycle()
+    const {
+  return false;
 }
 
 GLenum