Mac overlays: Clean up partial swap code

content/common/gpu/ca_layer_partial_damage_tree_mac.h

 // Copyright 2016 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 CONTENT_COMMON_GPU_CA_LAYER_PARTIAL_DAMAGE_TREE_MAC_H_
 #define CONTENT_COMMON_GPU_CA_LAYER_PARTIAL_DAMAGE_TREE_MAC_H_
 
 #include <IOSurface/IOSurface.h>
 #include <QuartzCore/QuartzCore.h>
 #include <deque>
 
 #include "base/mac/scoped_cftyperef.h"
-#include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_f.h"
 
 namespace content {
 
 class CALayerPartialDamageTree {
  public:
   CALayerPartialDamageTree(bool allow_partial_swap,
                            base::ScopedCFTypeRef<IOSurfaceRef> io_surface,
                            const gfx::Rect& pixel_frame_rect);
   ~CALayerPartialDamageTree();
 
   base::ScopedCFTypeRef<IOSurfaceRef> RootLayerIOSurface();
   void CommitCALayers(CALayer* superlayer,
                       scoped_ptr<CALayerPartialDamageTree> old_tree,
                       float scale_factor,
                       const gfx::Rect& pixel_damage_rect);
 
  private:
   class OverlayPlane;
 
-  void UpdateRootAndPartialDamagePlanes(CALayerPartialDamageTree* old_tree,
-                                        const gfx::RectF& pixel_damage_rect);
-  void UpdateRootAndPartialDamageCALayers(CALayer* superlayer,
-                                          float scale_factor);
+  // This will populate |partial_damage_planes_|, potentially re-using the
+  // CALayers and |partial_damage_planes_| from |old_tree|. After this function
+  // completes, the back() of |partial_damage_planes_| is the plane that will
+  // be updated this frame (and if it is empty, then the root plane will be
+  // updated).
+  void UpdatePartialDamagePlanes(CALayerPartialDamageTree* old_tree,
+                                 const gfx::Rect& pixel_damage_rect);
+
+  void UpdateRootAndPartialDamagePlanes(
+      scoped_ptr<CALayerPartialDamageTree> old_tree,
+      const gfx::Rect& pixel_damage_rect);
+
+  void UpdateCALayers(CALayer* superlayer, float scale_factor);
 
   const bool allow_partial_swap_;
-  linked_ptr<OverlayPlane> root_plane_;
-  std::deque<linked_ptr<OverlayPlane>> partial_damage_planes_;
+  scoped_ptr<OverlayPlane> root_plane_;
+  std::deque<scoped_ptr<OverlayPlane>> partial_damage_planes_;
 };
 
 }  // content
 
 #endif  // CONTENT_COMMON_GPU_CA_LAYER_PARTIAL_DAMAGE_TREE_MAC_H_