diff --git a/browser/base/content/test/general/browser_devices_get_user_media.js b/browser/base/content/test/general/browser_devices_get_user_media.js
index 1ec3bdcae34..806e14bbd38 100644
--- a/browser/base/content/test/general/browser_devices_get_user_media.js
+++ b/browser/base/content/test/general/browser_devices_get_user_media.js
@@ -593,6 +593,9 @@ let gTests = [
         yield promiseMessage(expectedMessage, gum);
 
         if (expectedMessage == "ok") {
+          expectObserverCalled("getUserMedia:request");
+          yield promiseNoPopupNotification("webRTC-shareDevices");
+          expectObserverCalled("getUserMedia:response:allow");
           expectObserverCalled("recording-device-events");
 
           // Check what's actually shared.
@@ -687,6 +690,8 @@ let gTests = [
       yield promiseMessage("ok", () => {
         content.wrappedJSObject.requestDevice(aRequestAudio, aRequestVideo);
       });
+      expectObserverCalled("getUserMedia:request");
+      expectObserverCalled("getUserMedia:response:allow");
       expectObserverCalled("recording-device-events");
       yield checkSharingUI();
 
diff --git a/browser/modules/webrtcUI.jsm b/browser/modules/webrtcUI.jsm
index f1eceece228..43dd0decd30 100644
--- a/browser/modules/webrtcUI.jsm
+++ b/browser/modules/webrtcUI.jsm
@@ -212,6 +212,38 @@ function prompt(aContentWindow, aCallID, aAudioRequested, aVideoRequested, aDevi
       if (aTopic != "showing")
         return false;
 
+      // DENY_ACTION is handled immediately by MediaManager, but handling
+      // of ALLOW_ACTION is delayed until the popupshowing event
+      // to avoid granting permissions automatically to background tabs.
+      if (aSecure) {
+        let perms = Services.perms;
+
+        let micPerm = perms.testExactPermission(uri, "microphone");
+        if (micPerm == perms.PROMPT_ACTION)
+          micPerm = perms.UNKNOWN_ACTION;
+
+        let camPerm = perms.testExactPermission(uri, "camera");
+        if (camPerm == perms.PROMPT_ACTION)
+          camPerm = perms.UNKNOWN_ACTION;
+
+        // We don't check that permissions are set to ALLOW_ACTION in this
+        // test; only that they are set. This is because if audio is allowed
+        // and video is denied persistently, we don't want to show the prompt,
+        // and will grant audio access immediately.
+        if ((!audioDevices.length || micPerm) && (!videoDevices.length || camPerm)) {
+          // All permissions we were about to request are already persistently set.
+          let allowedDevices = Cc["@mozilla.org/supports-array;1"]
+                                 .createInstance(Ci.nsISupportsArray);
+          if (videoDevices.length && camPerm == perms.ALLOW_ACTION)
+            allowedDevices.AppendElement(videoDevices[0]);
+          if (audioDevices.length && micPerm == perms.ALLOW_ACTION)
+            allowedDevices.AppendElement(audioDevices[0]);
+          Services.obs.notifyObservers(allowedDevices, "getUserMedia:response:allow", aCallID);
+          this.remove();
+          return true;
+        }
+      }
+
       function listDevices(menupopup, devices) {
         while (menupopup.lastChild)
           menupopup.removeChild(menupopup.lastChild);
diff --git a/dom/media/MediaManager.cpp b/dom/media/MediaManager.cpp
index 55eca714a11..f24ffbcdfbc 100644
--- a/dom/media/MediaManager.cpp
+++ b/dom/media/MediaManager.cpp
@@ -1498,14 +1498,6 @@ MediaManager::GetUserMedia(bool aPrivileged,
       rv = permManager->TestExactPermissionFromPrincipal(
         aWindow->GetExtantDoc()->NodePrincipal(), "microphone", &audioPerm);
       NS_ENSURE_SUCCESS(rv, rv);
-      if (audioPerm == nsIPermissionManager::PROMPT_ACTION) {
-        audioPerm = nsIPermissionManager::UNKNOWN_ACTION;
-      }
-      if (audioPerm == nsIPermissionManager::ALLOW_ACTION) {
-        if (!isHTTPS) {
-          audioPerm = nsIPermissionManager::UNKNOWN_ACTION;
-        }
-      }
     }
 
     uint32_t videoPerm = nsIPermissionManager::UNKNOWN_ACTION;
@@ -1513,33 +1505,11 @@ MediaManager::GetUserMedia(bool aPrivileged,
       rv = permManager->TestExactPermissionFromPrincipal(
         aWindow->GetExtantDoc()->NodePrincipal(), "camera", &videoPerm);
       NS_ENSURE_SUCCESS(rv, rv);
-      if (videoPerm == nsIPermissionManager::PROMPT_ACTION) {
-        videoPerm = nsIPermissionManager::UNKNOWN_ACTION;
-      }
-      if (videoPerm == nsIPermissionManager::ALLOW_ACTION) {
-        if (!isHTTPS) {
-          videoPerm = nsIPermissionManager::UNKNOWN_ACTION;
-        }
-      }
     }
 
-    if ((!IsOn(c.mAudio) || audioPerm != nsIPermissionManager::UNKNOWN_ACTION) &&
-        (!IsOn(c.mVideo) || videoPerm != nsIPermissionManager::UNKNOWN_ACTION)) {
-      // All permissions we were about to request already have a saved value.
-      if (IsOn(c.mAudio) && audioPerm == nsIPermissionManager::DENY_ACTION) {
-        c.mAudio.SetAsBoolean() = false;
-        runnable->SetContraints(c);
-      }
-      if (IsOn(c.mVideo) && videoPerm == nsIPermissionManager::DENY_ACTION) {
-        c.mVideo.SetAsBoolean() = false;
-        runnable->SetContraints(c);
-      }
-
-      if (!IsOn(c.mAudio) && !IsOn(c.mVideo)) {
-        return runnable->Denied(NS_LITERAL_STRING("PERMISSION_DENIED"));
-      }
-
-      return mMediaThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+    if ((!IsOn(c.mAudio) || audioPerm == nsIPermissionManager::DENY_ACTION) &&
+        (!IsOn(c.mVideo) || videoPerm == nsIPermissionManager::DENY_ACTION)) {
+      return runnable->Denied(NS_LITERAL_STRING("PERMISSION_DENIED"));
     }
 
     // Ask for user permission, and dispatch runnable (or not) when a response