clang-format: [JS] Let fat arrows have 'Equality' precedence.

This fixes a regression in literal formatting:

Before:
  aaaaaaaaaaaaa = {
    aaaaaaaaaaaaaaaaaaaaaaaaaaaa: (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
                                   aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) =>
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
  };

After:
  var aaaaaaaaaaaaaaaaaaaa = {
    aaaaaaaaaaaaaaaaaaaaaaaaaaaa:
        (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
         aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) =>
                aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
  };

Also apply no-else-after-return policy.

llvm-svn: 238942