cc: Remove tile ref counting in tile manager.

cc/resources/tile.cc

Index: cc/resources/tile.cc
diff --git a/cc/resources/tile.cc b/cc/resources/tile.cc
index 753ab0bdd8bfa3b925375d47ef79274dd9a253ce..d4837e9766261d59aac0ff3a8284fbbdc217c856 100644
--- a/cc/resources/tile.cc
+++ b/cc/resources/tile.cc
@@ -10,6 +10,8 @@
 
 namespace cc {
 
+uint64 Tile::s_next_id_ = 0;
+
 Tile::Tile(TileManager* tile_manager,
            PicturePileImpl* picture_pile,
            gfx::Size tile_size,
@@ -26,7 +28,8 @@ Tile::Tile(TileManager* tile_manager,
     opaque_rect_(opaque_rect),
     layer_id_(layer_id),
     source_frame_number_(source_frame_number),
-    can_use_lcd_text_(can_use_lcd_text) {
+    can_use_lcd_text_(can_use_lcd_text),
+    id_(s_next_id_++) {
   set_picture_pile(picture_pile);
   tile_manager_->RegisterTile(this);
 }