--- a/dom/media/tests/mochitest/test_getUserMedia_basicTabshare.html
+++ b/dom/media/tests/mochitest/test_getUserMedia_basicTabshare.html
@@ -18,18 +18,20 @@
    */
   runTest(function () {
     const isWinXP = navigator.userAgent.indexOf("Windows NT 5.1") != -1;
     if (IsMacOSX10_6orOlder() || isWinXP) {
         ok(true, "Screensharing disabled for OSX10.6 and WinXP");
         return;
     }
     var testVideo = createMediaElement('video', 'testVideo');
+    var pushPrefs = (...p) => SpecialPowers.pushPrefEnv({set: p});
 
     return Promise.resolve()
+      .then(() => pushPrefs(["media.getusermedia.browser.enabled", true]))
       .then(() => getUserMedia({
         video: { mediaSource: "browser",
                  scrollWithPage: true },
         fake: false
       }))
       .then(stream => {
         var playback = new LocalMediaStreamPlayback(testVideo, stream);
         return playback.playMediaWithDeprecatedStreamStop(false);

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -462,17 +462,17 @@ pref("media.peerconnection.video.enabled
 pref("media.navigator.video.max_fs", 12288); // Enough for 2048x1536
 pref("media.navigator.video.max_fr", 60);
 pref("media.navigator.video.h264.level", 31); // 0x42E01f - level 3.1
 pref("media.navigator.video.h264.max_br", 0);
 pref("media.navigator.video.h264.max_mbps", 0);
 pref("media.peerconnection.video.h264_enabled", false);
 pref("media.peerconnection.video.vp9_enabled", true);
 pref("media.getusermedia.aec", 1);
-pref("media.getusermedia.browser.enabled", true);
+pref("media.getusermedia.browser.enabled", false);
 #endif
 // Gonk typically captures at QVGA, and so min resolution is QQVGA or
 // 160x120; 100Kbps is plenty for that.
 // Desktop is typically VGA capture or more; and qm_select will not drop resolution
 // below 1/2 in each dimension (or so), so QVGA (320x200) is the lowest here usually.
 pref("media.peerconnection.video.min_bitrate", 0);
 pref("media.peerconnection.video.start_bitrate", 0);
 pref("media.peerconnection.video.max_bitrate", 0);