+ This only covers collapsing context according to the
diff preferences. Clicking on the control does nothing
in this change.
Change-Id: I82e07d1ba55630351b1f79db5f44ff81e2fafecd
+ This will eventually supplant gr-diff and gr-diff-side with a
simpler implementation once it reaches feature parity.
Change-Id: Ib0e5279daa8e61d79f8c2099613b80ef26d639f4