Merging r279268:

------------------------------------------------------------------------
r279268 | majnemer | 2016-08-19 09:37:40 -0700 (Fri, 19 Aug 2016) | 5 lines

[CloneFunction] Don't remove unrelated nodes from the CGSSC

CGSCC use a WeakVH to track call sites.  RAUW a call within a function
can result in that WeakVH getting confused about whether or not the call
site is still around.
------------------------------------------------------------------------

llvm-svn: 279477