Add DCLayerOverlayProcessor and supporting DCLayer structures.

components/display_compositor/compositor_overlay_candidate_validator_win.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_DISPLAY_COMPOSITOR_COMPOSITOR_OVERLAY_CANDIDATE_VALIDATOR_WIN_H_
 #define COMPONENTS_DISPLAY_COMPOSITOR_COMPOSITOR_OVERLAY_CANDIDATE_VALIDATOR_WIN_H_
 
 #include "base/macros.h"
 #include "components/display_compositor/compositor_overlay_candidate_validator.h"
 #include "components/display_compositor/display_compositor_export.h"
 
 namespace display_compositor {
 
 // This is a simple overlay candidate validator that promotes everything
 // possible to an overlay.
 class DISPLAY_COMPOSITOR_EXPORT CompositorOverlayCandidateValidatorWin
     : public CompositorOverlayCandidateValidator {
  public:
   CompositorOverlayCandidateValidatorWin();
   ~CompositorOverlayCandidateValidatorWin() override;
 
   void GetStrategies(cc::OverlayProcessor::StrategyList* strategies) override;
   void CheckOverlaySupport(cc::OverlayCandidateList* surfaces) override;
   bool AllowCALayerOverlays() override;
+  bool AllowDCLayerOverlays() override;
 
   void SetSoftwareMirrorMode(bool enabled) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CompositorOverlayCandidateValidatorWin);
 };
 
 }  // namespace display_compositor
 
 #endif  // COMPONENTS_DISPLAY_COMPOSITOR_COMPOSITOR_OVERLAY_CANDIDATE_VALIDATOR_WIN_H_