Bug 941457 - When clearing history, close all open tabs so the browser (including overlay buttons) is in a consistent state. r=mbrubeck, a=lsblakk
Bug 938107 - Wait for media state machine thread to shutdown during XPCOM shutdown before returning. r=roc, a=lsblakk

Add a MediaShutdownManager and have that as the only xpcom-shutdown
observer. This then shutsdown the MediaDecoders, and blocks waiting for
the media state machine's shared thread to complete shutdown before
exiting from the xpcom-shutdown observer. This ensures that the
MediaDecoder infrastructure does not use XPCOM on any thread after XPCOM
has shutdown, which is a logical error.
Bug 850372 - Delete session store backup during process suspend so that termination-from-suspended-state is treated as a normal shutdown. r=mbrubeck, a=lsblakk
Bug 947778 - Return early from SetEventHandler when ELM can't find the global jsobject. r=bz, a=lsblakk