Make PicturePile pile.

cc/picture_pile.h

Index: cc/picture_pile.h
diff --git a/cc/picture_pile.h b/cc/picture_pile.h
index 892fc392ac1eeb1a2afedf8c27491482308f91b9..11bfdfe6ee7d124fd75934354b6a22e63627c305 100644
--- a/cc/picture_pile.h
+++ b/cc/picture_pile.h
@@ -5,6 +5,8 @@
 #ifndef CC_PICTURE_PILE_H_
 #define CC_PICTURE_PILE_H_
 
+#include <list>
+
 #include "base/basictypes.h"
 #include "cc/cc_export.h"
 #include "cc/picture.h"
@@ -38,7 +40,13 @@ public:
   void PushPropertiesTo(PicturePileImpl* other);
 
 private:
-  std::vector<scoped_refptr<Picture> > pile_;
+  friend class PicturePileImpl;
+
+  void InvalidateRect(gfx::Rect invalidation);
+  void ResetPile(ContentLayerClient* painter, RenderingStats& stats);
+
+  typedef std::list<scoped_refptr<Picture> > Pile;
+  Pile pile_;
   gfx::Size size_;
 
   DISALLOW_COPY_AND_ASSIGN(PicturePile);