--- a/browser/modules/ContentWebRTC.jsm
+++ b/browser/modules/ContentWebRTC.jsm
@@ -68,20 +68,20 @@ this.ContentWebRTC = {
         break;
       }
       case "webrtc:Allow": {
         let callID = aMessage.data.callID;
         let contentWindow = Services.wm.getOuterWindowWithId(aMessage.data.windowID);
         let devices = contentWindow.pendingGetUserMediaRequests.get(callID);
         forgetGUMRequest(contentWindow, callID);
 
-        let allowedDevices = Cc["@mozilla.org/supports-array;1"]
-                               .createInstance(Ci.nsISupportsArray);
+        let allowedDevices = Cc["@mozilla.org/array;1"]
+                               .createInstance(Ci.nsIMutableArray);
         for (let deviceIndex of aMessage.data.devices)
-           allowedDevices.AppendElement(devices[deviceIndex]);
+           allowedDevices.appendElement(devices[deviceIndex], /*weak =*/ false);
 
         Services.obs.notifyObservers(allowedDevices, "getUserMedia:response:allow", callID);
         break;
       }
       case "webrtc:Deny":
         denyGUMRequest(aMessage.data);
         break;
       case "webrtc:StopSharing":

--- a/dom/media/MediaManager.cpp
+++ b/dom/media/MediaManager.cpp
@@ -16,17 +16,16 @@
 #ifdef MOZ_WIDGET_GONK
 #include "nsIAudioManager.h"
 #endif
 #include "nsIEventTarget.h"
 #include "nsIUUIDGenerator.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIPermissionManager.h"
 #include "nsIPopupWindowManager.h"
-#include "nsISupportsArray.h"
 #include "nsIDocShell.h"
 #include "nsIDocument.h"
 #include "nsISupportsPrimitives.h"
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsIIDNService.h"
 #include "nsNetCID.h"
 #include "nsNetUtil.h"
 #include "nsPrincipal.h"
@@ -2402,24 +2401,20 @@ if (privileged) {
       }
       if (!(*devices)->Length()) {
         RefPtr<MediaStreamError> error =
             new MediaStreamError(window, NS_LITERAL_STRING("NotFoundError"));
         onFailure->OnError(error);
         return;
       }
 
-      nsCOMPtr<nsISupportsArray> devicesCopy; // before we give up devices below
+      nsCOMPtr<nsIMutableArray> devicesCopy = nsArray::Create(); // before we give up devices below
       if (!askPermission) {
-        nsresult rv = NS_NewISupportsArray(getter_AddRefs(devicesCopy));
-        if (NS_WARN_IF(NS_FAILED(rv))) {
-          return;
-        }
         for (auto& device : **devices) {
-          rv = devicesCopy->AppendElement(device);
+          nsresult rv = devicesCopy->AppendElement(device, /*weak =*/ false);
           if (NS_WARN_IF(NS_FAILED(rv))) {
             return;
           }
         }
       }
 
       // Pass callbacks and MediaStreamListener along to GetUserMediaTask.
       RefPtr<GetUserMediaTask> task (new GetUserMediaTask(c, onSuccess.forget(),
@@ -3027,25 +3022,25 @@ MediaManager::Observe(nsISupports* aSubj
     mActiveCallbacks.Remove(key, getter_AddRefs(task));
     if (!task) {
       return NS_OK;
     }
 
     if (aSubject) {
       // A particular device or devices were chosen by the user.
       // NOTE: does not allow setting a device to null; assumes nullptr
-      nsCOMPtr<nsISupportsArray> array(do_QueryInterface(aSubject));
+      nsCOMPtr<nsIArray> array(do_QueryInterface(aSubject));
       MOZ_ASSERT(array);
       uint32_t len = 0;
-      array->Count(&len);
+      array->GetLength(&len);
       bool videoFound = false, audioFound = false;
       for (uint32_t i = 0; i < len; i++) {
-        nsCOMPtr<nsISupports> supports;
-        array->GetElementAt(i,getter_AddRefs(supports));
-        nsCOMPtr<nsIMediaDevice> device(do_QueryInterface(supports));
+        nsCOMPtr<nsIMediaDevice> device;
+        array->QueryElementAt(i, NS_GET_IID(nsIMediaDevice),
+                              getter_AddRefs(device));
         MOZ_ASSERT(device); // shouldn't be returning anything else...
         if (device) {
           nsString type;
           device->GetType(type);
           if (type.EqualsLiteral("video")) {
             if (!videoFound) {
               task->SetVideoDevice(static_cast<VideoDevice*>(device.get()));
               videoFound = true;

--- a/dom/media/MediaPermissionGonk.cpp
+++ b/dom/media/MediaPermissionGonk.cpp
@@ -1,21 +1,21 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "MediaManager.h"
 #include "MediaPermissionGonk.h"
 
+#include "nsArray.h"
 #include "nsCOMPtr.h"
 #include "nsIContentPermissionPrompt.h"
 #include "nsIDocument.h"
 #include "nsIDOMNavigatorUserMedia.h"
 #include "nsIStringEnumerator.h"
-#include "nsISupportsArray.h"
 #include "nsJSUtils.h"
 #include "nsQueryObject.h"
 #include "nsPIDOMWindow.h"
 #include "nsTArray.h"
 #include "GetUserMediaRequest.h"
 #include "mozilla/dom/PBrowserChild.h"
 #include "mozilla/dom/MediaStreamTrackBinding.h"
 #include "mozilla/dom/MediaStreamError.h"
@@ -62,22 +62,20 @@ FindDeviceByName(nsTArray<nsCOMPtr<nsIMe
   return nullptr;
 }
 
 // Helper function for notifying permission granted
 static nsresult
 NotifyPermissionAllow(const nsAString &aCallID, nsTArray<nsCOMPtr<nsIMediaDevice> > &aDevices)
 {
   nsresult rv;
-  nsCOMPtr<nsISupportsArray> array;
-  rv = NS_NewISupportsArray(getter_AddRefs(array));
-  NS_ENSURE_SUCCESS(rv, rv);
+  nsCOMPtr<nsIMutableArray> array = nsArray::Create();
 
   for (uint32_t i = 0; i < aDevices.Length(); ++i) {
-    rv = array->AppendElement(aDevices.ElementAt(i));
+    rv = array->AppendElement(aDevices.ElementAt(i), /*weak =*/ false);
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
   nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
   NS_ENSURE_TRUE(obs, NS_ERROR_FAILURE);
 
   return obs->NotifyObservers(array, "getUserMedia:response:allow",
                               aCallID.BeginReading());

--- a/mobile/android/chrome/content/WebrtcUI.js
+++ b/mobile/android/chrome/content/WebrtcUI.js
@@ -145,29 +145,29 @@ var WebrtcUI = {
       label: Strings.browser.GetStringFromName("getUserMedia.denyRequest.label"),
       callback: function() {
         Services.obs.notifyObservers(null, "getUserMedia:response:deny", aCallID);
       }
     },
     {
       label: Strings.browser.GetStringFromName("getUserMedia.shareRequest.label"),
       callback: function(checked /* ignored */, inputs) {
-        let allowedDevices = Cc["@mozilla.org/supports-array;1"].createInstance(Ci.nsISupportsArray);
+        let allowedDevices = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
 
         let audioId = 0;
         if (inputs && inputs.audioDevice != undefined)
           audioId = inputs.audioDevice;
         if (audioDevices[audioId])
-          allowedDevices.AppendElement(audioDevices[audioId]);
+          allowedDevices.appendElement(audioDevices[audioId], /*weak =*/ false);
 
         let videoId = 0;
         if (inputs && inputs.videoSource != undefined)
           videoId = inputs.videoSource;
         if (videoDevices[videoId]) {
-          allowedDevices.AppendElement(videoDevices[videoId]);
+          allowedDevices.appendElement(videoDevices[videoId], /*weak =*/ false);
           let perms = Services.perms;
           // Although the lifetime is "session" it will be removed upon
           // use so it's more of a one-shot.
           perms.add(aUri, "MediaManagerVideo", perms.ALLOW_ACTION, perms.EXPIRE_SESSION);
         }
 
         Services.obs.notifyObservers(allowedDevices, "getUserMedia:response:allow", aCallID);
       },