cc: Do GatherPixelRefs from skia at record time

cc/resources/picture.h

Index: cc/resources/picture.h
diff --git a/cc/resources/picture.h b/cc/resources/picture.h
index 8598fbf62b3c0a7ce983c9acd10737ef19e71d4a..a79a664f3f06aad7123d9afc3b39c6dbfb42982d 100644
--- a/cc/resources/picture.h
+++ b/cc/resources/picture.h
@@ -6,11 +6,14 @@
 #define CC_RESOURCES_PICTURE_H_
 
 #include <list>
+#include <utility>
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "cc/base/cc_export.h"
+#include "cc/base/hash_pair.h"
 #include "skia/ext/lazy_pixel_ref.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkPixelRef.h"
@@ -29,6 +32,10 @@ struct RenderingStats;
 class CC_EXPORT Picture
     : public base::RefCountedThreadSafe<Picture> {
  public:
+  typedef base::hash_map<
+      std::pair<int, int>,
+      std::list<skia::LazyPixelRef*> > PixelRefsMap;
+
   static scoped_refptr<Picture> Create(gfx::Rect layer_rect);
 
   const gfx::Rect& LayerRect() const { return layer_rect_; }
@@ -55,9 +62,27 @@ class CC_EXPORT Picture
               float contents_scale,
               bool enable_lcd_text);
 
-  void GatherPixelRefs(
-      const gfx::Rect& layer_rect,
-      std::list<skia::LazyPixelRef*>& pixel_ref_list);
+  class CC_EXPORT LazyPixelRefsIterator {
+   public:
+    LazyPixelRefsIterator();
+    LazyPixelRefsIterator(gfx::Rect layer_rect, const Picture* picture);
+    ~LazyPixelRefsIterator();
+
+    skia::LazyPixelRef* operator->() const { return current_pixel_ref_; }
+    skia::LazyPixelRef* operator*() const { return current_pixel_ref_; }
+    LazyPixelRefsIterator& operator++();
+    operator bool() const { return !!current_pixel_ref_; }
+
+   private:
+    const Picture* picture_;
+    std::list<skia::LazyPixelRef*> current_list_;
+    skia::LazyPixelRef* current_pixel_ref_;
+
+    gfx::Point min_point_;
+    gfx::Point max_point_;
+    int current_x_;
+    int current_y_;
+  };
 
  private:
   explicit Picture(gfx::Rect layer_rect);
@@ -65,9 +90,15 @@ class CC_EXPORT Picture
   // ownership to this picture.
   Picture(const skia::RefPtr<SkPicture>&,
           gfx::Rect layer_rect,
-          gfx::Rect opaque_rect);
+          gfx::Rect opaque_rect,
+          const PixelRefsMap& lazy_pixel_refs);
   ~Picture();
 
+  void GatherPixelRefsFromSkia(
+      const gfx::Rect& layer_rect,
+      std::list<skia::LazyPixelRef*>& pixel_ref_list);
+  void GatherAllPixelRefs();
+
   gfx::Rect layer_rect_;
   gfx::Rect opaque_rect_;
   skia::RefPtr<SkPicture> picture_;
@@ -75,7 +106,10 @@ class CC_EXPORT Picture
   typedef std::vector<scoped_refptr<Picture> > PictureVector;
   PictureVector clones_;
 
+  PixelRefsMap lazy_pixel_refs_;
+
   friend class base::RefCountedThreadSafe<Picture>;
+  friend class LazyPixelRefsIterator;
   DISALLOW_COPY_AND_ASSIGN(Picture);
 };