Refactor tests so we can just pass in text of a document for each test
Added tests for adding/deleting attributes character by character
* Added more tests for typing character by character and swapping children.
* Made typeAndExpect() and deleteAndExpect() check edits using the
  FakeDocument comparison stuff.
* Refactored common code out of typeAndExpect()/deleteAndExpect().
* Made it so we properly simulate what happens when the document was in
  an invalid state before typing (that logic happens in a code path that
  we don't call from the unit tests).
Merge pull request #4868 from adobe/nj/more-livehtml-tests

[LiveHTML] Add more tests