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

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index a8641ce66081bb8843e5db61234439a78d5ded15..b5342dfd453a27e18d70151e5656b3935a26001b 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -763,10 +763,6 @@
     twin_low_res = NULL;
   }
 
-  // TODO(enne): temporarily disable this optimization: http://crbug.com/335289
-  twin_high_res = NULL;
-  twin_low_res = NULL;
-
   // As a second pass, mark as required any visible high res tiles not filled in
   // by acceptable non-ideal tiles from the first pass.
   if (MarkVisibleTilesAsRequired(