Handling of trailing tabs in comments not idempotent

[Eckaaaaaat]

When formatting the following code

class Foo {
  void f() {
    int x = 0; // comment<TAB><TAB><TAB>
    return;
  }
}

where <TAB> represents ASCII 0x09 character the formatter removes the last tab character.
Thus when you apply the formatter again, it also removes the last tab.
Expected behavior would be either all trailing tabs removed or kept.

As Unicode reader discards last character if it is a whitespace preseving tabs would be difficult.