cc: Only register live tiles with the TileManager

cc/picture_layer_tiling.cc

Index: cc/picture_layer_tiling.cc
diff --git a/cc/picture_layer_tiling.cc b/cc/picture_layer_tiling.cc
index ca357a10b6d51dae26ed0b085fb604e148046051..5dd2dfef0099d9b51829b8b52522638a87881491 100644
--- a/cc/picture_layer_tiling.cc
+++ b/cc/picture_layer_tiling.cc
@@ -417,6 +417,7 @@ void PictureLayerTiling::UpdateTilePriorities(
     TileHandle* tile_handle = &find->second;
     Tile* tile = tile_handle->tile();
     tile->set_priority(tree, priority);
+    tile_handle->UnregisterFromTileManager();
   }
   last_prioritized_rect_ = inflated_rect;
 
@@ -442,6 +443,7 @@ void PictureLayerTiling::UpdateTilePriorities(
         continue;
       TileHandle* tile_handle = &find->second;
       Tile* tile = tile_handle->tile();
+      tile_handle->RegisterWithTileManager();
 
       gfx::Rect tile_bounds =
           tiling_data_.TileBounds(iter.index_x(), iter.index_y());
@@ -476,6 +478,7 @@ void PictureLayerTiling::UpdateTilePriorities(
         continue;
       TileHandle* tile_handle = &find->second;
       Tile* tile = tile_handle->tile();
+      tile_handle->RegisterWithTileManager();
 
       gfx::Rect tile_bounds =
           tiling_data_.TileBounds(iter.index_x(), iter.index_y());
@@ -543,9 +546,17 @@ scoped_ptr<base::Value> PictureLayerTiling::AsValue() const {
   return state.PassAs<base::Value>();
 }
 
-TileHandle::TileHandle(scoped_refptr<Tile> tile)
-    : tile_(tile),
-      managed_tile_state_(tile_->tile_manager()->RegisterTile(tile_)) {
+TileHandle::TileHandle(scoped_refptr<Tile> tile) : tile_(tile) {
+}
+
+void TileHandle::RegisterWithTileManager() {
+  if (managed_tile_state_.get())
+    return;
+  managed_tile_state_ = tile_->tile_manager()->RegisterTile(tile_);
+}
+
+void TileHandle::UnregisterFromTileManager() {
+  managed_tile_state_ = NULL;
 }
 
 }  // namespace cc