Revert of cc: Disable "activate to low res" optimization

cc/layers/picture_layer_impl_unittest.cc

Index: cc/layers/picture_layer_impl_unittest.cc
diff --git a/cc/layers/picture_layer_impl_unittest.cc b/cc/layers/picture_layer_impl_unittest.cc
index d3a6921ca911fcab3bd69a665bfe33a51ebbfaeb..c71fe5b6ab04423f391cfcc6f880be2489790124 100644
--- a/cc/layers/picture_layer_impl_unittest.cc
+++ b/cc/layers/picture_layer_impl_unittest.cc
@@ -1298,8 +1298,7 @@
   AssertNoTilesRequired(pending_layer_->LowResTiling());
 }
 
-// TODO(enne): temporarily disabled: http://crbug.com/335289
-TEST_F(PictureLayerImplTest, DISABLED_NothingRequiredIfAllHighResTilesShared) {
+TEST_F(PictureLayerImplTest, NothingRequiredIfAllHighResTilesShared) {
   gfx::Size layer_bounds(400, 400);
   gfx::Size tile_size(100, 100);
   SetupDefaultTreesWithFixedTileSize(layer_bounds, tile_size);
@@ -1317,8 +1316,7 @@
   AssertNoTilesRequired(pending_layer_->LowResTiling());
 }
 
-// TODO(enne): temporarily disabled: http://crbug.com/335289
-TEST_F(PictureLayerImplTest, DISABLED_NothingRequiredIfActiveMissingTiles) {
+TEST_F(PictureLayerImplTest, NothingRequiredIfActiveMissingTiles) {
   gfx::Size layer_bounds(400, 400);
   gfx::Size tile_size(100, 100);
   scoped_refptr<FakePicturePileImpl> pending_pile =