(bug 42189) merge runs of changes for RC.

When injecting repo changes into a client's recentchanges table,
combine runs of simmilar changes performed by the same user on
the same data item into one to avoid clutter.

Change-Id: I47a3246af0a6d7977a6ba01bd938afcf72abe2bb
Merge "(bug 42189) merge runs of changes for RC."