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 a56156b575373e34612d9baa74d08dbbf44a10b7..86e256d3ae9fbcc6a548ca6b00201263ad4e2a86 100644
--- a/cc/resources/picture.h
+++ b/cc/resources/picture.h
@@ -5,13 +5,17 @@
 #ifndef CC_RESOURCES_PICTURE_H_
 #define CC_RESOURCES_PICTURE_H_
 
-#include <list>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/hash_tables.h"
+#include "base/lazy_instance.h"
+#include "base/logging.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"
@@ -30,6 +34,10 @@ struct RenderingStats;
 class CC_EXPORT Picture
     : public base::RefCountedThreadSafe<Picture> {
  public:
+  typedef std::pair<int, int> PixelRefMapKey;
+  typedef std::vector<skia::LazyPixelRef*> PixelRefs;
+  typedef base::hash_map<PixelRefMapKey, PixelRefs> PixelRefMap;
+
   static scoped_refptr<Picture> Create(gfx::Rect layer_rect);
   static scoped_refptr<Picture> CreateFromBase64String(
       const std::string& encoded_string);
@@ -58,12 +66,41 @@ class CC_EXPORT Picture
               float contents_scale,
               bool enable_lcd_text);
 
-  void GatherPixelRefs(
-      gfx::Rect layer_rect,
-      std::list<skia::LazyPixelRef*>& pixel_ref_list);
-
   void AsBase64String(std::string* output) const;
 
+  class CC_EXPORT PixelRefIterator {
+   public:
+    PixelRefIterator();
+    PixelRefIterator(gfx::Rect layer_rect, const Picture* picture);
+    ~PixelRefIterator();
+
+    skia::LazyPixelRef* operator->() const {
+      DCHECK_LT(current_index_, current_pixel_refs_->size());
+      return (*current_pixel_refs_)[current_index_];
+    }
+
+    skia::LazyPixelRef* operator*() const {
+      DCHECK_LT(current_index_, current_pixel_refs_->size());
+      return (*current_pixel_refs_)[current_index_];
+    }
+
+    PixelRefIterator& operator++();
+    operator bool() const {
+      return current_index_ < current_pixel_refs_->size();
+    }
+
+   private:
+    static base::LazyInstance<PixelRefs> empty_pixel_refs_;
+    const Picture* picture_;
+    const PixelRefs* current_pixel_refs_;
+    unsigned current_index_;
+
+    gfx::Point min_point_;
+    gfx::Point max_point_;
+    int current_x_;
+    int current_y_;
+  };
+
  private:
   explicit Picture(gfx::Rect layer_rect);
   Picture(const std::string& encoded_string, bool* success);
@@ -71,9 +108,13 @@ 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 PixelRefMap& pixel_refs);
   ~Picture();
 
+  void GatherPixelRefsFromSkia(gfx::Rect query_rect, PixelRefs* pixel_refs);
+  void GatherAllPixelRefs();
+
   gfx::Rect layer_rect_;
   gfx::Rect opaque_rect_;
   skia::RefPtr<SkPicture> picture_;
@@ -81,7 +122,13 @@ class CC_EXPORT Picture
   typedef std::vector<scoped_refptr<Picture> > PictureVector;
   PictureVector clones_;
 
+  PixelRefMap pixel_refs_;
+  gfx::Point min_pixel_cell_;
+  gfx::Point max_pixel_cell_;
+  gfx::Size cell_size_;
+
   friend class base::RefCountedThreadSafe<Picture>;
+  friend class PixelRefIterator;
   DISALLOW_COPY_AND_ASSIGN(Picture);
 };