Add DCLayerOverlayProcessor and supporting DCLayer structures.

components/display_compositor/compositor_overlay_candidate_validator_mac.mm

 // Copyright 2015 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.
 
 #include "components/display_compositor/compositor_overlay_candidate_validator_mac.h"
 
 #include <stddef.h>
 
 namespace display_compositor {
 
 CompositorOverlayCandidateValidatorMac::CompositorOverlayCandidateValidatorMac(
     bool ca_layer_disabled)
     : software_mirror_active_(false), ca_layer_disabled_(ca_layer_disabled) {}
 
 CompositorOverlayCandidateValidatorMac::
     ~CompositorOverlayCandidateValidatorMac() {}
 
 void CompositorOverlayCandidateValidatorMac::GetStrategies(
     cc::OverlayProcessor::StrategyList* strategies) {}
 
 bool CompositorOverlayCandidateValidatorMac::AllowCALayerOverlays() {
   return !ca_layer_disabled_ && !software_mirror_active_;
 }
 
+bool CompositorOverlayCandidateValidatorMac::AllowDCLayerOverlays() {
+  return false;
+}
+
 void CompositorOverlayCandidateValidatorMac::CheckOverlaySupport(
     cc::OverlayCandidateList* surfaces) {}
 
 void CompositorOverlayCandidateValidatorMac::SetSoftwareMirrorMode(
     bool enabled) {
   software_mirror_active_ = enabled;
 }
 
 }  // namespace display_compositor