Fix overflow testing in sbrk. am: 1944780b62 am: 3a5ebf3154  -s ours
am: d95336ac42

* commit 'd95336ac42e910e9dd11f01f5af65e8e1f4505cb':
  Fix overflow testing in sbrk.

Change-Id: I60e5637cf560af8b95ccc585f86c2f0fa04481f1