cc: Do GatherPixelRefs from skia at record time

cc/resources/picture_pile_impl.h

 // Copyright 2012 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_RESOURCES_PICTURE_PILE_IMPL_H_
 #define CC_RESOURCES_PICTURE_PILE_IMPL_H_
 
 #include <list>
 #include <map>
 #include <vector>
@@ skipping 19 matching lines @@
 
   // Raster a subrect of this PicturePileImpl into the given canvas.
   // It's only safe to call paint on a cloned version.
   // It is assumed that contents_scale has already been applied to this canvas.
   // Return value is the total number of pixels rasterized.
   int64 Raster(
       SkCanvas* canvas,
       gfx::Rect canvas_rect,
       float contents_scale);
 
-  void GatherPixelRefs(
-      gfx::Rect content_rect,
-      float contents_scale,
-      std::list<skia::LazyPixelRef*>& pixel_refs);
-
   skia::RefPtr<SkPicture> GetFlattenedPicture();
 
   struct CC_EXPORT Analysis {
     Analysis();
     ~Analysis();
 
     bool is_solid_color;
     bool is_transparent;
     bool has_text;
     bool is_cheap_to_raster;
     SkColor solid_color;
 
     skia::AnalysisCanvas::LazyPixelRefList lazy_pixel_refs;
   };
 
   void AnalyzeInRect(gfx::Rect content_rect,
                      float contents_scale,
                      Analysis* analysis);
 
+  class CC_EXPORT PixelRefIterator {
+   public:
+    PixelRefIterator(gfx::Rect content_rect,
+                     float contents_scale,
+                     const PicturePileImpl* picture_pile);
+    ~PixelRefIterator();
+
+    skia::LazyPixelRef* operator->() const { return *pixel_ref_iterator_; }
+    skia::LazyPixelRef* operator*() const { return *pixel_ref_iterator_; }
+    PixelRefIterator& operator++();
+    operator bool() const { return pixel_ref_iterator_; }
+
+   private:
+    bool AdvanceToTileWithPictures();
+    void AdvanceToPictureWithPixelRefs();
+
+    const PicturePileImpl* picture_pile_;
+    gfx::Rect layer_rect_;
+    TilingData::Iterator tile_iterator_;
+    Picture::PixelRefIterator pixel_ref_iterator_;
+    const PictureList* picture_list_;
+    PictureList::const_iterator picture_list_iterator_;
+  };
+
  protected:
   friend class PicturePile;
+  friend class PixelRefIterator;
 
   explicit PicturePileImpl(bool enable_lcd_text);
   PicturePileImpl(const PicturePileBase* other, bool enable_lcd_text);
   virtual ~PicturePileImpl();
 
  private:
   class ClonesForDrawing {
    public:
     ClonesForDrawing(const PicturePileImpl* pile, int num_threads);
     ~ClonesForDrawing();
@@ skipping 14 matching lines @@
   // instance.  This member variable must be last so that other member
   // variables have already been initialized and can be clonable.
   const ClonesForDrawing clones_for_drawing_;
 
   DISALLOW_COPY_AND_ASSIGN(PicturePileImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PICTURE_PILE_IMPL_H_