clang-format: [JS] Add a special case for indenting function literals.

Before:
  var func =
      function() {
        doSomething();
      };

After:
  var func =
      function() {
    doSomething();
  };

This is a very narrow special case which fixes most of the discrepency
with what our users do. In the long run, we should try to come up with
a more generic fix for indenting these.

llvm-svn: 240014