Adds an aria-label to added and removed rows marking the row as "added"
or "removed" for screen readers. As part of this change, the <tr>
elements that make up the diff are now focusable.
Test plan:
- Somewhat included as a part of testing this functionality is the use
of WCT's a11ySuite function[1]. This will be introduced in a later
change.
[1] https://goo.gl/P15eE6
Bug: Issue 6435
Change-Id: I676fc171d404ca6e8e9276965192b1452595fa61
40ea3ade99