clang-format: Fix indentation corner case.

Before:
  aaaaaaaaaa(aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
                 .aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);
  aaaaaaaaaa = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
                   .aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa();

After:
  aaaaaaaaaa(aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
                 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
                 .aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);
  aaaaaaaaaa = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
                   aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
                   .aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa();

Probably still not ideal, but should be a step into the right direction.

llvm-svn: 197557