Bug 1161036 part 2. Only force-enable dom cache in test_serviceworker_interfaces if we're having to force-enable servicewceworkers too. r=bkelly

dom/workers/test/serviceworkers/test_serviceworker_interfaces.html

@@ -94,12 +94,28 @@
 
   SimpleTest.waitForExplicitFinish();
   onload = function() {
-    SpecialPowers.pushPrefEnv({"set": [
+    // The handling of "dom.caches.enabled" here is a bit complicated.  What we
+    // want to happen is that Cache is always enabled in service workers.  So
+    // if service workers are disabled by default we want to force on both
+    // service workers and "dom.caches.enabled".  But if service workers are
+    // enabled by default, we do not want to mess with the "dom.caches.enabled"
+    // value, since that would defeat the purpose of the test.  Use a subframe
+    // to decide whether service workers are enabled by default, so we don't
+    // force creation of our own Navigator object before our prefs are set.
+    var prefs = [
       ["dom.serviceWorkers.exemptFromPerDomainMax", true],
       ["dom.serviceWorkers.enabled", true],
       ["dom.serviceWorkers.testing.enabled", true],
-      ["dom.caches.enabled", true]
-    ]}, runTest);
+    ];
+
+    var subframe = document.createElement("iframe");
+    document.body.appendChild(subframe);
+    if (!("serviceWorker" in subframe.contentWindow.navigator)) {
+	prefs.push(["dom.caches.enabled", true]);
+    }
+    subframe.remove();
+
+    SpecialPowers.pushPrefEnv({"set": prefs}, runTest);
   };
 </script>
 </body>

dom/workers/test/serviceworkers/test_serviceworker_interfaces.js

@@ -91,9 +91,9 @@ var interfaceNamesInGlobalScope =
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "BroadcastChannel",
 // IMPORTANT: Do not change this list without review from a DOM peer!
-    { name: "Cache", release: false },
+    "Cache",
 // IMPORTANT: Do not change this list without review from a DOM peer!
-    { name: "CacheStorage", release: false },
+    "CacheStorage",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "Client",
 // IMPORTANT: Do not change this list without review from a DOM peer!