diff --git a/dom/media/PeerConnection.js b/dom/media/PeerConnection.js
index 9987e2ace28..234be094b5c 100644
--- a/dom/media/PeerConnection.js
+++ b/dom/media/PeerConnection.js
@@ -22,8 +22,10 @@ const PC_MANAGER_CID = Components.ID("{7293e901-2be3-4c02-b4bd-cbef6fc24f78}");
 // Global list of PeerConnection objects, so they can be cleaned up when
 // a page is torn down. (Maps inner window ID to an array of PC objects).
 function GlobalPCList() {
-  this._list = {};
+  this._list = [];
   Services.obs.addObserver(this, "inner-window-destroyed", true);
+  Services.obs.addObserver(this, "profile-change-net-teardown", true);
+  Services.obs.addObserver(this, "network:offline-about-to-go-offline", true);
 }
 GlobalPCList.prototype = {
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver,
@@ -63,19 +65,32 @@ GlobalPCList.prototype = {
   },
 
   observe: function(subject, topic, data) {
-    if (topic != "inner-window-destroyed") {
-      return;
+    if (topic == "inner-window-destroyed") {
+      let winID = subject.QueryInterface(Ci.nsISupportsPRUint64).data;
+      if (this._list[winID]) {
+        this._list[winID].forEach(function(pc) {
+          pc._pc.close(false);
+          delete pc._observer;
+          pc._pc = null;
+        });
+        delete this._list[winID];
+      }
+    } else if (topic == "profile-change-net-teardown" ||
+               topic == "network:offline-about-to-go-offline") {
+      // Delete all peerconnections on shutdown - synchronously (we need
+      // them to be done deleting transports before we return)!
+      // Also kill them if "Work Offline" is selected - more can be created 
+      // while offline, but attempts to connect them should fail.
+      let array;
+      while ((array = this._list.pop()) != undefined) {
+        array.forEach(function(pc) {
+          pc._pc.close(true);
+          delete pc._observer;
+          pc._pc = null;
+        });
+      };
     }
-    let winID = subject.QueryInterface(Ci.nsISupportsPRUint64).data;
-    if (this._list[winID]) {
-      this._list[winID].forEach(function(pc) {
-        pc._pc.close();
-        delete pc._observer;
-        pc._pc = null;
-      });
-      delete this._list[winID];
-    }
-  }
+  },
 };
 let _globalPCList = new GlobalPCList();
 
@@ -453,7 +468,7 @@ PeerConnection.prototype = {
   close: function() {
     this._queueOrRun({
       func: this._pc.close,
-      args: [],
+      args: [false],
       wait: false
     });
     this._closed = true;
diff --git a/dom/media/bridge/IPeerConnection.idl b/dom/media/bridge/IPeerConnection.idl
index 8b36635fb4f..9873a761705 100644
--- a/dom/media/bridge/IPeerConnection.idl
+++ b/dom/media/bridge/IPeerConnection.idl
@@ -65,7 +65,7 @@ interface IPeerConnectionObserver : nsISupports
   void foundIceCandidate(in string candidate);
 };
 
-[scriptable, uuid(f6819246-f5af-40f2-ab82-e166d5da7ba0)]
+[scriptable, uuid(c86903c7-0a2e-42b4-903c-1518f03b9ba5)]
 interface IPeerConnection : nsISupports
 {
   const unsigned long kHintAudio = 0x00000001;
@@ -113,7 +113,7 @@ interface IPeerConnection : nsISupports
   void addIceCandidate(in string candidate, in string mid, in unsigned short level);
 
   /* Puts the SIPCC engine back to 'kIdle', shuts down threads, deletes state */
-  void close();
+  void close(in bool isSynchronous);
 
   /* Attributes */
   readonly attribute string localDescription;
diff --git a/media/webrtc/signaling/src/peerconnection/PeerConnectionImpl.cpp b/media/webrtc/signaling/src/peerconnection/PeerConnectionImpl.cpp
index fc1d7d1db6d..1f76c5b4d71 100644
--- a/media/webrtc/signaling/src/peerconnection/PeerConnectionImpl.cpp
+++ b/media/webrtc/signaling/src/peerconnection/PeerConnectionImpl.cpp
@@ -278,7 +278,7 @@ PeerConnectionImpl::PeerConnectionImpl()
 
 PeerConnectionImpl::~PeerConnectionImpl()
 {
-  Close();
+  Close(false);
   // Since this and Initialize() occur on MainThread, they can't both be
   // running at once
   // Might be more optimal to release off a timer (and XPCOM Shutdown)
@@ -935,7 +935,7 @@ PeerConnectionImpl::GetIceState(uint32_t* aState)
 }
 
 NS_IMETHODIMP
-PeerConnectionImpl::Close()
+PeerConnectionImpl::Close(bool aIsSynchronous)
 {
   if (mCall != NULL)
     mCall->endCall();
@@ -944,7 +944,7 @@ PeerConnectionImpl::Close()
     mDataConnection->CloseAll();
 #endif
 
-  ShutdownMedia();
+  ShutdownMedia(aIsSynchronous);
 
   // DataConnection will need to stay alive until all threads/runnables exit
 
@@ -952,7 +952,7 @@ PeerConnectionImpl::Close()
 }
 
 void
-PeerConnectionImpl::ShutdownMedia()
+PeerConnectionImpl::ShutdownMedia(bool aIsSynchronous)
 {
   // Check that we are on the main thread.
   if (mThread) {
@@ -969,10 +969,15 @@ PeerConnectionImpl::ShutdownMedia()
   // This avoids reentrancy issues with the garbage collector.
   // Note that no media calls may be made after this point
   // because we have removed the pointer.
+  // For the aIsSynchronous case, we *know* the PeerConnection is
+  // still alive, and are shutting it down on network teardown/etc, so
+  // recursive GC isn't an issue. (Recursive GC should assert)
+
   // Forget the reference so that we can transfer it to
   // SelfDestruct().
   RUN_ON_THREAD(mThread, WrapRunnable(mMedia.forget().get(),
-        &PeerConnectionMedia::SelfDestruct), NS_DISPATCH_NORMAL);
+                                      &PeerConnectionMedia::SelfDestruct),
+                aIsSynchronous ? NS_DISPATCH_SYNC : NS_DISPATCH_NORMAL);
 }
 
 void
diff --git a/media/webrtc/signaling/src/peerconnection/PeerConnectionImpl.h b/media/webrtc/signaling/src/peerconnection/PeerConnectionImpl.h
index 333242fdc83..ea3f1f296c8 100644
--- a/media/webrtc/signaling/src/peerconnection/PeerConnectionImpl.h
+++ b/media/webrtc/signaling/src/peerconnection/PeerConnectionImpl.h
@@ -166,7 +166,7 @@ private:
   }
 
   // Shut down media. Called on any thread.
-  void ShutdownMedia();
+  void ShutdownMedia(bool isSynchronous);
 
   nsresult MakeMediaStream(uint32_t aHint, nsIDOMMediaStream** aStream);
   nsresult MakeRemoteSource(nsDOMMediaStream* aStream, RemoteSourceStreamInfo** aInfo);