Backed out changeset 664c633802d4 (bug 1423220) for frequently failing mochitest dom/html/test/test_fullscreen-api-race.html (bug 1445330). a=backout

browser/app/profile/firefox.js

@@ -1541,12 +1541,8 @@ pref("browser.tabs.remote.desktopbehavior", true);
 
 // For speculatively warming up tabs to improve perceived
 // performance while using the async tab switcher.
-#if defined(NIGHTLY_BUILD)
-pref("browser.tabs.remote.warmup.enabled", true);
-#else
+// Disabled until bug 1397426 is fixed.
 pref("browser.tabs.remote.warmup.enabled", false);
-#endif
-
 pref("browser.tabs.remote.warmup.maxTabs", 3);
 pref("browser.tabs.remote.warmup.unloadDelayMs", 2000);
 

dom/base/test/browser_bug1303838.js

@@ -16,18 +16,6 @@
 const BASE_URL = "http://mochi.test:8888/browser/dom/base/test/";
 
 add_task(async function() {
-  // On Linux, in our test automation, the mouse cursor floats over
-  // the first tab, which causes it to be warmed up when tab warming
-  // is enabled. The TabSwitchDone event doesn't fire until the warmed
-  // tab is evicted, which is after a few seconds. That means that
-  // this test ends up taking longer than we'd like, since its waiting
-  // for the TabSwitchDone event between tab switches.
-  //
-  // So now we make sure that warmed tabs are evicted very shortly
-  // after warming to avoid the test running too long.
-  await SpecialPowers.pushPrefEnv({
-    set: [["browser.tabs.remote.warmup.unloadDelayMs", 50]],
-  });
   await testLinkClick(false, false);
   await testLinkClick(false, true);
   await testLinkClick(true, false);