When a user taps a line number in a diff, the cursor is moved to that
line and that side of the diff. However, if the user taps the text
content of a diff, the cursor was not moved. With this change, the
cursor is moved to the appropriate line and side of a diff when either
is tapped.
Bug: Issue 4215
Change-Id: I47d24f678f487eb3f8173ea5572865a589d845e4