--- a/ipc/glue/MessageChannel.cpp
+++ b/ipc/glue/MessageChannel.cpp
@@ -765,16 +765,20 @@ MessageChannel::Echo(Message* aMsg)
 bool
 MessageChannel::Send(Message* aMsg)
 {
     if (aMsg->size() >= kMinTelemetryMessageSize) {
         Telemetry::Accumulate(Telemetry::IPC_MESSAGE_SIZE,
                               nsDependentCString(aMsg->name()), aMsg->size());
     }
 
+    MOZ_RELEASE_ASSERT(!aMsg->is_sync());
+    // We never send an async high priority message.
+    MOZ_RELEASE_ASSERT(aMsg->priority() != IPC::Message::PRIORITY_HIGH);
+
     CxxStackFrame frame(*this, OUT_MESSAGE, aMsg);
 
     nsAutoPtr<Message> msg(aMsg);
     AssertWorkerThread();
     mMonitor->AssertNotCurrentThreadOwns();
     if (MSG_ROUTING_NONE == msg->routing_id()) {
         ReportMessageRouteError("MessageChannel::Send");
         return false;
@@ -836,16 +840,17 @@ MessageChannel::ShouldDeferMessage(const
 {
     // Never defer messages that have the highest priority, even async
     // ones. This is safe because only the child can send these messages, so
     // they can never nest.
     if (aMsg.priority() == IPC::Message::PRIORITY_URGENT)
         return false;
 
     // Unless they're urgent, we always defer async messages.
+    // Note that we never send an async high priority message.
     if (!aMsg.is_sync()) {
         MOZ_RELEASE_ASSERT(aMsg.priority() == IPC::Message::PRIORITY_NORMAL);
         return true;
     }
 
     int msgPrio = aMsg.priority();
     int waitingPrio = AwaitingSyncReplyPriority();
 

--- a/js/src/ds/MemoryProtectionExceptionHandler.cpp
+++ b/js/src/ds/MemoryProtectionExceptionHandler.cpp
@@ -12,26 +12,28 @@
 #if defined(XP_WIN)
 # include "jswin.h"
 #elif defined(XP_LINUX)
 # include <signal.h>
 # include <sys/types.h>
 # include <unistd.h>
 #elif defined(XP_DARWIN)
 # include <mach/mach.h>
+# include <unistd.h>
 #endif
 
 #ifdef ANDROID
 # include <android/log.h>
 #endif
 
 #include "ds/SplayTree.h"
 
 #include "threading/LockGuard.h"
 #include "threading/Mutex.h"
+#include "threading/Thread.h"
 
 namespace js {
 
 /*
  * A class to store the addresses of the regions recognized as protected
  * by this exception handler. We use a splay tree to store these addresses.
  */
 class ProtectedRegionTree

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -531,20 +531,20 @@ pref("media.navigator.audio.full_duplex"
 
 pref("dom.webaudio.enabled", true);
 
 #if !defined(ANDROID)
 pref("media.getusermedia.screensharing.enabled", true);
 #endif
 
 #ifdef RELEASE_BUILD
-pref("media.getusermedia.screensharing.allowed_domains", "webex.com,*.webex.com,ciscospark.com,*.ciscospark.com,projectsquared.com,*.projectsquared.com,*.room.co,room.co,beta.talky.io,talky.io,*.clearslide.com,appear.in,*.appear.in,tokbox.com,*.tokbox.com,*.sso.francetelecom.fr,*.si.francetelecom.fr,*.sso.infra.ftgroup,*.multimedia-conference.orange-business.com,*.espacecollaboration.orange-business.com,free.gotomeeting.com,g2m.me,*.g2m.me,*.mypurecloud.com,*.mypurecloud.com.au,spreed.me,*.spreed.me,*.spreed.com,air.mozilla.org,*.circuit.com,*.yourcircuit.com,circuit.siemens.com,yourcircuit.siemens.com,circuitsandbox.net,*.unify.com,tandi.circuitsandbox.net,*.ericsson.net,*.cct.ericsson.net,*.opentok.com,*.conf.meetecho.com,meet.jit.si,*.meet.jit.si,web.stage.speakeasyapp.net,web.speakeasyapp.net,*.hipchat.me,*.beta-wspbx.com,*.wspbx.com,*.unifiedcloudit.com,*.smartboxuc.com,*.smartbox-uc.com,*.panterranetworks.com,pexipdemo.com,*.pexipdemo.com,pex.me,*.pex.me,*.rd.pexip.com,1click.io,*.1click.io,*.fuze.com,*.fuzemeeting.com,*.thinkingphones.com,gotomeeting.com,*.gotomeeting.com,gotowebinar.com,*.gotowebinar.com,gototraining.com,*.gototraining.com,citrix.com,*.citrix.com,expertcity.com,*.expertcity.com,citrixonline.com,*.citrixonline.com,g2m.me,*.g2m.me,gotomeet.me,*.gotomeet.me,gotomeet.at,*.gotomeet.at,miriadaxdes.miriadax.net,certificacion.miriadax.net,miriadax.net,*.wire.com,sylaps.com,*.sylaps.com");
+pref("media.getusermedia.screensharing.allowed_domains", "webex.com,*.webex.com,ciscospark.com,*.ciscospark.com,projectsquared.com,*.projectsquared.com,*.room.co,room.co,beta.talky.io,talky.io,*.clearslide.com,appear.in,*.appear.in,tokbox.com,*.tokbox.com,*.sso.francetelecom.fr,*.si.francetelecom.fr,*.sso.infra.ftgroup,*.multimedia-conference.orange-business.com,*.espacecollaboration.orange-business.com,free.gotomeeting.com,g2m.me,*.g2m.me,*.mypurecloud.com,*.mypurecloud.com.au,spreed.me,*.spreed.me,*.spreed.com,air.mozilla.org,*.circuit.com,*.yourcircuit.com,circuit.siemens.com,yourcircuit.siemens.com,circuitsandbox.net,*.unify.com,tandi.circuitsandbox.net,*.ericsson.net,*.cct.ericsson.net,*.opentok.com,*.conf.meetecho.com,meet.jit.si,*.meet.jit.si,web.stage.speakeasyapp.net,web.speakeasyapp.net,*.hipchat.me,*.beta-wspbx.com,*.wspbx.com,*.unifiedcloudit.com,*.smartboxuc.com,*.smartbox-uc.com,*.panterranetworks.com,pexipdemo.com,*.pexipdemo.com,pex.me,*.pex.me,*.rd.pexip.com,1click.io,*.1click.io,*.fuze.com,*.fuzemeeting.com,*.thinkingphones.com,gotomeeting.com,*.gotomeeting.com,gotowebinar.com,*.gotowebinar.com,gototraining.com,*.gototraining.com,citrix.com,*.citrix.com,expertcity.com,*.expertcity.com,citrixonline.com,*.citrixonline.com,g2m.me,*.g2m.me,gotomeet.me,*.gotomeet.me,gotomeet.at,*.gotomeet.at,miriadaxdes.miriadax.net,certificacion.miriadax.net,miriadax.net,*.wire.com,sylaps.com,*.sylaps.com,bluejeans.com,*.bluejeans.com,*.a.bluejeans.com");
 #else
  // includes Mozilla's test domain: mozilla.github.io (not intended for release)
-pref("media.getusermedia.screensharing.allowed_domains", "mozilla.github.io,webex.com,*.webex.com,ciscospark.com,*.ciscospark.com,projectsquared.com,*.projectsquared.com,*.room.co,room.co,beta.talky.io,talky.io,*.clearslide.com,appear.in,*.appear.in,tokbox.com,*.tokbox.com,*.sso.francetelecom.fr,*.si.francetelecom.fr,*.sso.infra.ftgroup,*.multimedia-conference.orange-business.com,*.espacecollaboration.orange-business.com,free.gotomeeting.com,g2m.me,*.g2m.me,*.mypurecloud.com,*.mypurecloud.com.au,spreed.me,*.spreed.me,*.spreed.com,air.mozilla.org,*.circuit.com,*.yourcircuit.com,circuit.siemens.com,yourcircuit.siemens.com,circuitsandbox.net,*.unify.com,tandi.circuitsandbox.net,*.ericsson.net,*.cct.ericsson.net,*.opentok.com,*.conf.meetecho.com,meet.jit.si,*.meet.jit.si,web.stage.speakeasyapp.net,web.speakeasyapp.net,*.hipchat.me,*.beta-wspbx.com,*.wspbx.com,*.unifiedcloudit.com,*.smartboxuc.com,*.smartbox-uc.com,*.panterranetworks.com,pexipdemo.com,*.pexipdemo.com,pex.me,*.pex.me,*.rd.pexip.com,1click.io,*.1click.io,*.fuze.com,*.fuzemeeting.com,*.thinkingphones.com,gotomeeting.com,*.gotomeeting.com,gotowebinar.com,*.gotowebinar.com,gototraining.com,*.gototraining.com,citrix.com,*.citrix.com,expertcity.com,*.expertcity.com,citrixonline.com,*.citrixonline.com,g2m.me,*.g2m.me,gotomeet.me,*.gotomeet.me,gotomeet.at,*.gotomeet.at,miriadaxdes.miriadax.net,certificacion.miriadax.net,miriadax.net,*.wire.com,sylaps.com,*.sylaps.com");
+pref("media.getusermedia.screensharing.allowed_domains", "mozilla.github.io,webex.com,*.webex.com,ciscospark.com,*.ciscospark.com,projectsquared.com,*.projectsquared.com,*.room.co,room.co,beta.talky.io,talky.io,*.clearslide.com,appear.in,*.appear.in,tokbox.com,*.tokbox.com,*.sso.francetelecom.fr,*.si.francetelecom.fr,*.sso.infra.ftgroup,*.multimedia-conference.orange-business.com,*.espacecollaboration.orange-business.com,free.gotomeeting.com,g2m.me,*.g2m.me,*.mypurecloud.com,*.mypurecloud.com.au,spreed.me,*.spreed.me,*.spreed.com,air.mozilla.org,*.circuit.com,*.yourcircuit.com,circuit.siemens.com,yourcircuit.siemens.com,circuitsandbox.net,*.unify.com,tandi.circuitsandbox.net,*.ericsson.net,*.cct.ericsson.net,*.opentok.com,*.conf.meetecho.com,meet.jit.si,*.meet.jit.si,web.stage.speakeasyapp.net,web.speakeasyapp.net,*.hipchat.me,*.beta-wspbx.com,*.wspbx.com,*.unifiedcloudit.com,*.smartboxuc.com,*.smartbox-uc.com,*.panterranetworks.com,pexipdemo.com,*.pexipdemo.com,pex.me,*.pex.me,*.rd.pexip.com,1click.io,*.1click.io,*.fuze.com,*.fuzemeeting.com,*.thinkingphones.com,gotomeeting.com,*.gotomeeting.com,gotowebinar.com,*.gotowebinar.com,gototraining.com,*.gototraining.com,citrix.com,*.citrix.com,expertcity.com,*.expertcity.com,citrixonline.com,*.citrixonline.com,g2m.me,*.g2m.me,gotomeet.me,*.gotomeet.me,gotomeet.at,*.gotomeet.at,miriadaxdes.miriadax.net,certificacion.miriadax.net,miriadax.net,*.wire.com,sylaps.com,*.sylaps.com,bluejeans.com,*.bluejeans.com,*.a.bluejeans.com");
 #endif
 // OS/X 10.6 and XP have screen/window sharing off by default due to various issues - Caveat emptor
 pref("media.getusermedia.screensharing.allow_on_old_platforms", false);
 
 pref("media.getusermedia.audiocapture.enabled", false);
 
 // TextTrack WebVTT Region extension support.
 pref("media.webvtt.regions.enabled", false);