Overlays: Remove special casing of primary overlay plane

cc/output/output_surface.h

Index: cc/output/output_surface.h
diff --git a/cc/output/output_surface.h b/cc/output/output_surface.h
index 66d1c79bd696961a7fb5e9514c4b0394e67fca66..bb6a59e7ecde237fe827fcd91af98d53454a34ac 100644
--- a/cc/output/output_surface.h
+++ b/cc/output/output_surface.h
@@ -151,6 +151,9 @@ class CC_EXPORT OutputSurface : public base::trace_event::MemoryDumpProvider {
   // Get the class capable of informing cc of hardware overlay capability.
   virtual OverlayCandidateValidator* GetOverlayCandidateValidator() const;
 
+  // Returns true if a main image overlay plane should be scheduled.
+  virtual bool IsDisplayedAsOverlayPlane() const;
+
   // Get the texture for the main image's overlay.
   virtual unsigned GetOverlayTextureId() const;