Mac Overlays: Allow multiple overlays with sandwich strategy

cc/output/overlay_strategy_common.h

 // 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.
 
 #ifndef CC_OUTPUT_OVERLAY_STRATEGY_COMMON_H_
 #define CC_OUTPUT_OVERLAY_STRATEGY_COMMON_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/output/overlay_candidate.h"
 #include "cc/output/overlay_processor.h"
 
 namespace cc {
 class IOSurfaceDrawQuad;
 class OverlayCandidate;
 class OverlayCandidateValidator;
 class StreamVideoDrawQuad;
 class TextureDrawQuad;
 
+enum OverlayResult {
+  DID_NOT_CREATE_OVERLAY,
+  CREATED_OVERLAY_STOP_LOOKING,
+  CREATED_OVERLAY_KEEP_LOOKING,
+};
+
 class CC_EXPORT OverlayStrategyCommonDelegate {
  public:
   virtual ~OverlayStrategyCommonDelegate() {}
-  virtual bool TryOverlay(OverlayCandidateValidator* capability_checker,
-                          RenderPassList* render_passes_in_draw_order,
-                          OverlayCandidateList* candidate_list,
-                          const OverlayCandidate& candidate,
-                          QuadList::Iterator iter,
-                          float device_scale_factor) = 0;
+
+  // Check if |candidate| can be promoted into an overlay. If so, add it to
+  // |candidate_list| and update the quads in |render_passes_in_draw_order|
+  // as necessary. When returning CREATED_OVERLAY_KEEP_LOOKING, |iter| is
+  // updated to point to the next quad to evaluate.
+  virtual OverlayResult TryOverlay(
+      OverlayCandidateValidator* capability_checker,
+      RenderPassList* render_passes_in_draw_order,
+      OverlayCandidateList* candidate_list,
+      const OverlayCandidate& candidate,
+      QuadList::Iterator* iter,
+      float device_scale_factor) = 0;
 };
 
 class CC_EXPORT OverlayStrategyCommon : public OverlayProcessor::Strategy {
  public:
   explicit OverlayStrategyCommon(OverlayCandidateValidator* capability_checker,
                                  OverlayStrategyCommonDelegate* delegate);
   ~OverlayStrategyCommon() override;
 
   bool Attempt(RenderPassList* render_passes_in_draw_order,
                OverlayCandidateList* candidate_list,
@@ skipping 20 matching lines @@
 
  private:
   OverlayCandidateValidator* capability_checker_;
   scoped_ptr<OverlayStrategyCommonDelegate> delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(OverlayStrategyCommon);
 };
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OVERLAY_STRATEGY_COMMON_H_