Comments before closing brace are indented incorrectly

[bamarsha]

The formatter indents this program incorrectly:

namespace Foo {
    function Bar() : Unit {
        let x = 0;
        // Hello world
    }
}

Output:

namespace Foo {
    function Bar() : Unit {
        let x = 0;
    // Hello world
    }
}

[kuzminrobin]

TODO(kuzminrobin): Master the Formatter, Update the ReadMe if necessary. Ask: Scott, Bettina.