Switch contacts sync to an EasSyncBase.

Also includes some changes to EasSyncBase and friends to
accomodate this conversion.

Change-Id: I6b58bbdd9c62120371a92d1a2deddbab302d1b13
(cherry picked from commit 52c9dfbbed3860d9b7dfc60fae466f620464151c)
9 files changed