Fix a PCH crash bug where we kept a reference inside a DenseMap while the map was getting modified.

No test case, sorry. It's one of those bugs where it's really really hard to make one. rdar://9910862.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@137383 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed