This patch was to fix a reported Hangouts deadlock/freezing issue
in VP8 encoder(issue 27232610). The original encoder loopfilter
synchronization happened in the following frame, which was prone
to causing problems in some complex use cases. This patch simplified
the synchronization logic.

More testing needs to be done.

Change-Id: I38fd3f35d11f98fae1e44546aa5e4c6d6e19c4be