Bug 1222495 - Get dom/workers/test/test_suspend.html working with e10s and B2G. r=khuey

dom/workers/test/mochitest.ini

@@ -187,7 +187,6 @@ skip-if = buildapp == 'b2g' # b2g(Failed to load script: relativeLoad_import.js)
 skip-if = (toolkit == 'gonk' && debug) # Bug 1176223
 [test_simpleThread.html]
 [test_suspend.html]
-skip-if = buildapp == 'b2g' || e10s # b2g(test timed out, might need more time) b2g-debug(test timed out, might need more time) b2g-desktop(test timed out, might need more time) e10s(Bug 1222495 - Sets preferences directly)
 [test_terminate.html]
 [test_terminateSyncXHR.html]
 [test_threadErrors.html]

dom/workers/test/test_suspend.html

@@ -31,27 +31,15 @@
   var oldMessageCount;
   var waitCount = 0;
 
-  function setCachePref(enabled) {
-    var prefBranch = SpecialPowers.Cc["@mozilla.org/preferences-service;1"]
-                                  .getService(SpecialPowers.Ci.nsIPrefBranch);
-    if (enabled) {
-      prefBranch.setBoolPref("browser.sessionhistory.cache_subframes", true);
-    }
-    else {
-      try {
-        prefBranch.clearUserPref("browser.sessionhistory.cache_subframes");
-      } catch (e) { /* Pref didn't exist, meh */ }
-    }
-  }
-
   function finishTest() {
     if (finished) {
       return;
     }
     finished = true;
-    setCachePref(false);
-    iframe.terminateWorker();
-    SimpleTest.finish();
+    SpecialPowers.flushPrefEnv(function () {
+      iframe.terminateWorker();
+      SimpleTest.finish();
+    });
   }
 
   function waitInterval() {
@@ -84,12 +72,13 @@
     is(String(iframe.location), "about:blank", "Wrong url!");
     is(suspended, false, "Already suspended?");
     is(resumed, false, "Already resumed?");
-    setCachePref(false);
-    suspended = true;
-    var iframeElement = document.getElementById("workerFrame");
-    iframeElement.onload = badOnloadCallback;
-    oldMessageCount = lastCount;
-    interval = setInterval(waitInterval, 1000);
+    SpecialPowers.popPrefEnv(function () {
+      suspended = true;
+      var iframeElement = document.getElementById("workerFrame");
+      iframeElement.onload = badOnloadCallback;
+      oldMessageCount = lastCount;
+      interval = setInterval(waitInterval, 1000);
+    });
   }
 
   function messageCallback(data) {
@@ -102,12 +91,13 @@
          "Got good data, lastCount = " + lastCount + ", data = " + data);
       lastCount = data;
       if (lastCount == 25) {
-        setCachePref(true);
-        iframe.location = "about:blank";
-        // We want suspend_iframe.html to go into bfcache, so we need to flush
-        // out all pending notifications. Otherwise, if they're flushed too
-        // late, they could kick us out of the bfcache again.
-        iframe.document.body.offsetTop;
+        SpecialPowers.pushPrefEnv({"set": [["browser.sessionhistory.cache_subframes", true]]}, function () {
+          iframe.location = "about:blank";
+          // We want suspend_iframe.html to go into bfcache, so we need to flush
+          // out all pending notifications. Otherwise, if they're flushed too
+          // late, they could kick us out of the bfcache again.
+          iframe.document.body.offsetTop;
+        });
       }
       return;
     }