function mustBecomeBoundary(editorState, changeType) {
	  var lastChangeType = editorState.getLastChangeType();
	  return changeType !== lastChangeType || changeType !== 'insert-characters' && changeType !== 'backspace-character' && changeType !== 'delete-character';
	}
Return whether a change should be considered a boundary state, given
the previous change type. Allows us to discard potential boundary states
during standard typing or deletion behavior.