Fix indentation for case: // comment.

Before:
switch (x) {
case 1:
    // Do amazing stuff
    {
  g();
  f();
}
}

After:
switch (x) {
case 1:
  // Do amazing stuff
  {
    g();
    f();
  }
}

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177420 91177308-0d34-0410-b5e6-96231b3b80d8