Fix uninitialized variable use bug found by the clairvoyant static analyzer.

Commit::canReplaceText would not initialize its out 'Len' parameter before
returning true and it would be used uninitialized in Commit::replaceText.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159306 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed