Merge changes Iddd42d75,Ifb2d7b35 into nyc-dev
am: 9e95b36

* commit '9e95b3697ebae72173804cc867557fa20caf7ef3':
  Reuse HUseListNode<>s when replacing instruction or input.
  Use iterators "before" the use node in HUserRecord<>.

Change-Id: I0b75ea4892646fdf5c8f0889d2e3d2ab92befc81