diff --git a/browser/base/content/test/webrtc/browser_devices_get_user_media_in_frame.js b/browser/base/content/test/webrtc/browser_devices_get_user_media_in_frame.js
index 3f56a532d968..32f8bba32751 100644
--- a/browser/base/content/test/webrtc/browser_devices_get_user_media_in_frame.js
+++ b/browser/base/content/test/webrtc/browser_devices_get_user_media_in_frame.js
@@ -130,15 +130,15 @@ var gTests = [
 {
   desc: "getUserMedia audio+video: reloading a frame updates the sharing UI",
   run: async function checkUpdateWhenReloading() {
-    // We'll share only the mic in the first frame, then share both in the
+    // We'll share only the cam in the first frame, then share both in the
     // second frame, then reload the second frame. After each step, we'll check
     // the UI is in the correct state.
 
     let promise = promisePopupNotificationShown("webRTC-shareDevices");
-    await promiseRequestDevice(true, false, "frame1");
+    await promiseRequestDevice(false, true, "frame1");
     await promise;
     await expectObserverCalled("getUserMedia:request");
-    checkDeviceSelectors(true, false);
+    checkDeviceSelectors(false, true);
 
     let indicator = promiseIndicatorWindow();
     await promiseMessage("ok", () => {
@@ -146,11 +146,11 @@ var gTests = [
     });
     await expectObserverCalled("getUserMedia:response:allow");
     await expectObserverCalled("recording-device-events");
-    Assert.deepEqual((await getMediaCaptureState()), {audio: true},
-                     "expected microphone to be shared");
+    Assert.deepEqual((await getMediaCaptureState()), {video: true},
+                     "expected camera to be shared");
 
     await indicator;
-    await checkSharingUI({video: false, audio: true});
+    await checkSharingUI({video: true, audio: false});
     await expectNoObserverCalled();
 
     promise = promisePopupNotificationShown("webRTC-shareDevices");
@@ -176,7 +176,7 @@ var gTests = [
     await promise;
 
     await expectObserverCalled("recording-window-ended");
-    await checkSharingUI({video: false, audio: true});
+    await checkSharingUI({video: true, audio: false});
     await expectNoObserverCalled();
 
     await closeStream(false, "frame1");
diff --git a/dom/ipc/TabParent.cpp b/dom/ipc/TabParent.cpp
index ed5f870a5d1a..d84976072367 100644
--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -164,7 +164,7 @@ TabParent::TabParent(nsIContentParent* aManager,
   , mInitedByParent(false)
   , mTabId(aTabId)
   , mCreatingWindow(false)
-  , mCursor(nsCursor(-1))
+  , mCursor(eCursorInvalid)
   , mTabSetsCursor(false)
   , mHasContentOpener(false)
 #ifdef DEBUG
@@ -1131,7 +1131,7 @@ TabParent::SendRealMouseEvent(WidgetMouseEvent& aEvent)
       if (mCustomCursor) {
         widget->SetCursor(mCustomCursor,
                           mCustomCursorHotspotX, mCustomCursorHotspotY);
-      } else if (mCursor != nsCursor(-1)) {
+      } else if (mCursor != eCursorInvalid) {
         widget->SetCursor(mCursor);
       }
     } else if (eMouseExitFromWidget == aEvent.mMessage) {
@@ -1787,7 +1787,7 @@ TabParent::RecvSetCustomCursor(const nsCString& aCursorData,
                                const uint32_t& aHotspotY,
                                const bool& aForce)
 {
-  mCursor = nsCursor(-1);
+  mCursor = eCursorInvalid;
 
   nsCOMPtr<nsIWidget> widget = GetWidget();
   if (widget) {
diff --git a/dom/media/MediaManager.cpp b/dom/media/MediaManager.cpp
index 7e3ed762360d..a06296086a28 100644
--- a/dom/media/MediaManager.cpp
+++ b/dom/media/MediaManager.cpp
@@ -1232,8 +1232,13 @@ public:
                                                  self->mSourceListener->GetPrincipalHandle());
         if (NS_FAILED(rv)) {
           nsString log;
-          log.AssignASCII("Starting audio failed");
-          error = new MediaMgrError(NS_LITERAL_STRING("InternalError"), log);
+          if (rv == NS_ERROR_NOT_AVAILABLE) {
+            log.AssignASCII("Concurrent mic process limit.");
+            error = new MediaMgrError(NS_LITERAL_STRING("NotReadableError"), log);
+          } else {
+            log.AssignASCII("Starting audio failed");
+            error = new MediaMgrError(NS_LITERAL_STRING("InternalError"), log);
+          }
         }
       }
 
diff --git a/dom/media/webrtc/MediaEngineWebRTCAudio.cpp b/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
index 3f3b6074fd4b..ff77065b09fa 100644
--- a/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
+++ b/dom/media/webrtc/MediaEngineWebRTCAudio.cpp
@@ -474,6 +474,13 @@ MediaEngineWebRTCMicrophoneSource::Start(SourceMediaStream *aStream,
     return NS_ERROR_FAILURE;
   }
 
+  // Until we fix bug 1400488 we need to block a second tab (OuterWindow)
+  // from opening an already-open device.  If it's the same tab, they
+  // will share a Graph(), and we can allow it.
+  if (!mSources.IsEmpty() && aStream->Graph() != mSources[0]->Graph()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
   {
     MonitorAutoLock lock(mMonitor);
     mSources.AppendElement(aStream);
diff --git a/dom/workers/RuntimeService.cpp b/dom/workers/RuntimeService.cpp
index 526008df5406..e294ca6db05e 100644
--- a/dom/workers/RuntimeService.cpp
+++ b/dom/workers/RuntimeService.cpp
@@ -885,9 +885,9 @@ InitJSContextForWorker(WorkerPrivate* aWorkerPrivate, JSContext* aWorkerCx)
   // This is the real place where we set the max memory for the runtime.
   for (uint32_t index = 0; index < ArrayLength(gcSettings); index++) {
     const JSSettings::JSGCSetting& setting = gcSettings[index];
-    if (setting.IsSet()) {
+    if (setting.key.isSome()) {
       NS_ASSERTION(setting.value, "Can't handle 0 values!");
-      JS_SetGCParameter(aWorkerCx, setting.key, setting.value);
+      JS_SetGCParameter(aWorkerCx, *setting.key, setting.value);
     }
   }
 
@@ -1935,7 +1935,7 @@ RuntimeService::Init()
   }
 
   // Initialize JSSettings.
-  if (!sDefaultJSSettings.gcSettings[0].IsSet()) {
+  if (sDefaultJSSettings.gcSettings[0].key.isNothing()) {
     sDefaultJSSettings.contextOptions = JS::ContextOptions();
     sDefaultJSSettings.chrome.maxScriptRuntime = -1;
     sDefaultJSSettings.chrome.compartmentOptions.behaviors().setVersion(JSVERSION_DEFAULT);
diff --git a/dom/workers/Workers.h b/dom/workers/Workers.h
index aa25ccffd578..fbcccd293f91 100644
--- a/dom/workers/Workers.h
+++ b/dom/workers/Workers.h
@@ -9,6 +9,7 @@
 
 #include "jsapi.h"
 #include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/Mutex.h"
 #include <stdint.h>
 #include "nsAutoPtr.h"
@@ -102,25 +103,12 @@ struct JSSettings
 
   struct JSGCSetting
   {
-    JSGCParamKey key;
+    mozilla::Maybe<JSGCParamKey> key;
     uint32_t value;
 
     JSGCSetting()
-    : key(static_cast<JSGCParamKey>(-1)), value(0)
+    : key(), value(0)
     { }
-
-    bool
-    IsSet() const
-    {
-      return key != static_cast<JSGCParamKey>(-1);
-    }
-
-    void
-    Unset()
-    {
-      key = static_cast<JSGCParamKey>(-1);
-      value = 0;
-    }
   };
 
   // There are several settings that we know we need so it makes sense to
@@ -166,11 +154,11 @@ struct JSSettings
 
     for (uint32_t index = 0; index < ArrayLength(gcSettings); index++) {
       JSSettings::JSGCSetting& setting = gcSettings[index];
-      if (setting.key == aKey) {
+      if (setting.key.isSome() && *setting.key == aKey) {
         foundSetting = &setting;
         break;
       }
-      if (!firstEmptySetting && !setting.IsSet()) {
+      if (!firstEmptySetting && setting.key.isNothing()) {
         firstEmptySetting = &setting;
       }
     }
@@ -183,13 +171,13 @@ struct JSSettings
           return false;
         }
       }
-      foundSetting->key = aKey;
+      foundSetting->key = mozilla::Some(aKey);
       foundSetting->value = aValue;
       return true;
     }
 
     if (foundSetting) {
-      foundSetting->Unset();
+      foundSetting->key.reset();
       return true;
     }
 
diff --git a/media/libcubeb/README_MOZILLA b/media/libcubeb/README_MOZILLA
index d449c51794e9..29a1468c5028 100644
--- a/media/libcubeb/README_MOZILLA
+++ b/media/libcubeb/README_MOZILLA
@@ -5,4 +5,4 @@ Makefile.in build files for the Mozilla build system.
 
 The cubeb git repository is: git://github.com/kinetiknz/cubeb.git
 
-The git commit ID used was 09a90a7817bc3d76723065fdc6b53c542fbed402 (2017-09-13 18:39:50 +0200)
+The git commit ID used was ac532ad4f0defaf7a397db64c2c42d2665cd06e9 (2017-09-17 08:23:45 +1200)
diff --git a/media/libcubeb/src/cubeb_audiounit.cpp b/media/libcubeb/src/cubeb_audiounit.cpp
index 1ac430671275..979a577305f3 100644
--- a/media/libcubeb/src/cubeb_audiounit.cpp
+++ b/media/libcubeb/src/cubeb_audiounit.cpp
@@ -733,7 +733,12 @@ audiounit_property_listener_callback(AudioObjectID id, UInt32 address_count,
         break;
       case kAudioDevicePropertyDataSource: {
           LOG("Event[%u] - mSelector == kAudioHardwarePropertyDataSource for id=%d", (unsigned int) i, id);
-          switch_side |= DEV_INPUT;
+          if (stm->input_unit) {
+            switch_side |= DEV_INPUT;
+          }
+          if (stm->output_unit) {
+            switch_side |= DEV_OUTPUT;
+          }
         }
         break;
       default:
diff --git a/testing/mozharness/scripts/release/generate-checksums.py b/testing/mozharness/scripts/release/generate-checksums.py
index f6a8f5c99d0e..796f57fa2698 100644
--- a/testing/mozharness/scripts/release/generate-checksums.py
+++ b/testing/mozharness/scripts/release/generate-checksums.py
@@ -72,6 +72,7 @@ class ChecksumsGenerator(BaseScript, VirtualenvMixin, SigningMixin, VCSMixin, Bu
             require_config_file=False,
             config={
                 "virtualenv_modules": [
+                    "pip==1.5.5",
                     "boto",
                 ],
                 "virtualenv_path": "venv",
diff --git a/widget/PuppetWidget.cpp b/widget/PuppetWidget.cpp
index 3f0e6e49f9a6..40070f5fb11d 100644
--- a/widget/PuppetWidget.cpp
+++ b/widget/PuppetWidget.cpp
@@ -1012,7 +1012,7 @@ PuppetWidget::SetCursor(imgIContainer* aCursor,
     return NS_ERROR_FAILURE;
   }
 
-  mCursor = nsCursor(-1);
+  mCursor = eCursorInvalid;
   mCustomCursor = aCursor;
   mCursorHotspotX = aHotspotX;
   mCursorHotspotY = aHotspotY;
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index dcb9a3fc9756..37b6aae4c3d0 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -1623,7 +1623,7 @@ nsWindow::SetCursor(imgIContainer* aCursor,
         return window->SetCursor(aCursor, aHotspotX, aHotspotY);
     }
 
-    mCursor = nsCursor(-1);
+    mCursor = eCursorInvalid;
 
     // Get the image's current frame
     GdkPixbuf* pixbuf = nsImageToPixbuf::ImageToPixbuf(aCursor);
diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
index 73851ac64137..7b8cdcc97608 100644
--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -211,8 +211,12 @@ enum nsCursor {   ///(normal cursor,       usually rendered as an arrow)
                 eCursor_ns_resize,
                 eCursor_ew_resize,
                 eCursor_none,
-                // This one better be the last one in this list.
-                eCursorCount
+                // This one is used for array sizing, and so better be the last
+                // one in this list...
+                eCursorCount,
+
+                // ...except for this one.
+                eCursorInvalid = eCursorCount + 1
                 };
 
 enum nsTopLevelWidgetZPlacement { // for PlaceBehind()
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 1e658c99e07f..b4d915014a18 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -3020,7 +3020,7 @@ nsWindow::SetCursor(imgIContainer* aCursor,
   rv = nsWindowGfx::CreateIcon(aCursor, true, aHotspotX, aHotspotY, size, &cursor);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  mCursor = nsCursor(-1);
+  mCursor = eCursorInvalid;
   ::SetCursor(cursor);
 
   NS_IF_RELEASE(sCursorImgContainer);
@@ -7179,7 +7179,7 @@ void nsWindow::OnDestroy()
   }
 
   // Destroy any custom cursor resources.
-  if (mCursor == -1)
+  if (mCursor == eCursorInvalid)
     SetCursor(eCursor_standard);
 
   if (mCompositorWidgetDelegate) {