b/9857766
If we currently have zero messages (i.e. initial sync of
a new account) we will load the most recent 100 messages.
On subsequent syncs, we will load more recent messages
until either:
1. We have loaded 100 and not yet past any of the messages
we already had locally, or
2. We encounter messages that we already had locally, and
then load "deltaMessageCount" additional messages past
the ones we have locally.
Change-Id: I8b34409dcdaceff2d2e1906174241a74f2331688
b177af7534