[Support] Allow multiple paired calls to {start,stop}Timer()

Differential Revision: http://reviews.llvm.org/D15619

Reviewed-by: rafael

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256258 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed