2d2a3c405e5472f27b96484b068f51c34ee5e6cb added diff against to the change
screen2. However base revision is lost when side by side view is closed.
This change fixes that.
Conflicts:
gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.java
Change-Id: I7f74760fde96469a60556f657923a3936d6516c7