Async BLAST Sync[3/N]: Push sync-id around

We push the syncId around via MSG_RESIZED and via
finishDrawing. We can see the finishDrawing change
is no-op, as it's not used on the server side. Likewise
we can see the MSG_RESIZED change is noop, since even if it
is received, it wont be used unless we call relayoutWindow
in which case it will be overwritten by the one used there. This
change is thus a noop until we actually remove relayout window.

Bug: 161810301
Bug: 175861051
Bug: 175861127
Bug: 200285149
Change-Id: I30627ddad805731109aebeeaf6c74867dcd1ecca