Add hints for potential overlay promotion on android.

cc/output/overlay_candidate_validator.h

 // Copyright 2014 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_CANDIDATE_VALIDATOR_H_
 #define CC_OUTPUT_OVERLAY_CANDIDATE_VALIDATOR_H_
 
 #include <vector>
 
 #include "cc/base/cc_export.h"
+#include "cc/base/resource_id.h"
 #include "cc/output/overlay_candidate.h"
 #include "cc/output/overlay_processor.h"
 
 namespace cc {
 
 // This class that can be used to answer questions about possible overlay
 // configurations for a particular output device.
 class CC_EXPORT OverlayCandidateValidator {
  public:
   // Populates a list of strategies that may work with this validator.
   virtual void GetStrategies(OverlayProcessor::StrategyList* strategies) = 0;
 
   // Returns true if draw quads can be represented as CALayers (Mac only).
   virtual bool AllowCALayerOverlays() = 0;
 
   // A list of possible overlay candidates is presented to this function.
   // The expected result is that those candidates that can be in a separate
   // plane are marked with |overlay_handled| set to true, otherwise they are
   // to be traditionally composited. Candidates with |overlay_handled| set to
   // true must also have their |display_rect| converted to integer
   // coordinates if necessary.
   virtual void CheckOverlaySupport(OverlayCandidateList* surfaces) = 0;
 
+  // Called before beginning a new pass for overlay promotion to clear out any
+  // promotable resources.  One must CheckoverlaySupport() again.
+  virtual void ClearPromotableResources() {}
+
+  // Returns whether |resource_id| is promotable.
+  virtual bool IsResourcePromotable(ResourceId resource_id);

[piman, 2016/11/23 00:37:25]

Super nit: in the context of OverlayCandidateValidator, IsResourcePromotable
suggests "this resource can be put in an overlay" as in "right now", whereas I
think you mean "this resource would be ok to put in an overlay, but only if it's
switched to SurfaceView, but it isn't right now". Not sure what is the best name
to convey the concept...

[liberato (no reviews please), 2016/12/01 20:59:11]

i've since moved the set into OverlayCandidateList, since it was a little weird
to have this statefulness here.

named the set 'promotable_resource_hints_'

+
   virtual ~OverlayCandidateValidator() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OVERLAY_CANDIDATE_VALIDATOR_H_