SF: Don't pop pending state into mCurrentState

Let mCurrentState always represent the most up to date state, even if
there are transactions we don't want to commit yet. Past snapshots of
the state are kept in mPendingState. In doTransaction(), grab the
correct pending state from mPendingState, but save it to a local copy
that gets committed rather than overriding mCurrentState.

Bug 27205755

Change-Id: Ib0ea809da1954409787c52b8f41d7963a57a6a4c