Fix invalid formatting with spaces before trailing comments.

In google style, trailing comments are separated by two spaces. This
patch fixes the counting of these spaces and prevents clang-format from
creating a line with 81 columns.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174879 91177308-0d34-0410-b5e6-96231b3b80d8