Bug 1076820 - Redraw on resize performance for content is pretty bad with e10s r=billm

Modern OSs adjust process scheduling based on CPU-boundedness and Interface-boundedness.  A process performing a lot of UI tasks requires lower-latency than a CPU-bound process.  For this reason, at least on Windows (but probably also Linux and Mac), in e10s, resize events are sent at a much higher rate than non-e10s, where the main process has to do the work to respond to them.  This was supposed to be handled by the 'compress' option in IPDL but its duplicate-event test was very imprecise - it only tested the *oldest* message in the queue.  This patch searches the messagequeue/deque to remove *any* duplicate.  deque::erase is linear but this is a very uncommon case - currently only two compressed IPDL messages exist in the entire code base.  Also, these queues are small.