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 625f95cbc86b46b10bf45dcb0f8444a29ea491e0..31c94e0fab757d93ebd7346bee727539bb12d7ad 100644
--- a/cc/resources/tile.h
+++ b/cc/resources/tile.h
@@ -32,6 +32,10 @@ class CC_EXPORT Tile : public base::RefCounted<Tile> {
        int source_frame_number,
        bool can_use_lcd_text);
 
+  uint64 id() const {
+    return id_;
+  }
+
   PicturePileImpl* picture_pile() {
     return picture_pile_.get();
   }
@@ -141,6 +145,9 @@ class CC_EXPORT Tile : public base::RefCounted<Tile> {
   int source_frame_number_;
   bool can_use_lcd_text_;
 
+  uint64 id_;
+  static uint64 s_next_id_;
+
   DISALLOW_COPY_AND_ASSIGN(Tile);
 };