cc: Remove tile ref counting in tile manager.

cc/resources/tile.h

Index: cc/resources/tile.h
diff --git a/cc/resources/tile.h b/cc/resources/tile.h
index 449ca4604a12b1178429040dff3c9d0f48081657..408d4b13403180aab50a0be0eeb06381f27b13bf 100644
--- a/cc/resources/tile.h
+++ b/cc/resources/tile.h
@@ -17,10 +17,11 @@
 namespace cc {
 
 class PicturePileImpl;
-class Tile;
 
 class CC_EXPORT Tile : public base::RefCounted<Tile> {
  public:
+  typedef uint64 Id;
+
   Tile(TileManager* tile_manager,
        PicturePileImpl* picture_pile,
        gfx::Size tile_size,
@@ -31,6 +32,10 @@ class CC_EXPORT Tile : public base::RefCounted<Tile> {
        int source_frame_number,
        bool can_use_lcd_text);
 
+  Id id() const {
+    return id_;
+  }
+
   PicturePileImpl* picture_pile() {
     return picture_pile_.get();
   }
@@ -141,6 +146,9 @@ class CC_EXPORT Tile : public base::RefCounted<Tile> {
   int source_frame_number_;
   bool can_use_lcd_text_;
 
+  Id id_;
+  static Id s_next_id_;
+
   DISALLOW_COPY_AND_ASSIGN(Tile);
 };