clang-format: Fix corner case in one-per-line formatting.

Before (example is JS, but also applies to C++):
  return [
    aaaa()
        .bbbbbbbb('A'),
    aaaa().bbbbbbbb('B'),
    aaaa().bbbbbbbb('C'),
  ];

After:
  return [
    aaaa().bbbbbbbb('A'),
    aaaa().bbbbbbbb('B'),
    aaaa().bbbbbbbb('C'),
  ];

llvm-svn: 257079