Bug 1478390. Simplify service worker script cache code now that sandbox nsIGlobalObjects hold on to their JS global. r=mrbkap

dom/serviceworkers/ServiceWorkerScriptCache.cpp

@@ -41,26 +41,21 @@ namespace serviceWorkerScriptCache {
 
 namespace {
 
-// XXX A sandbox nsIGlobalObject does not preserve its reflector, so |aSandbox|
-// must be kept alive as long as the CacheStorage if you want to ensure that
-// the CacheStorage will continue to work. Failures will manifest as errors
-// like "JavaScript error: , line 0: TypeError: The expression cannot be
-// converted to return the specified type."
 already_AddRefed<CacheStorage>
-CreateCacheStorage(JSContext* aCx, nsIPrincipal* aPrincipal, ErrorResult& aRv,
-                   JS::MutableHandle<JSObject*> aSandbox)
+CreateCacheStorage(JSContext* aCx, nsIPrincipal* aPrincipal, ErrorResult& aRv)
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(aPrincipal);
 
   nsIXPConnect* xpc = nsContentUtils::XPConnect();
   MOZ_ASSERT(xpc, "This should never be null!");
-  aRv = xpc->CreateSandbox(aCx, aPrincipal, aSandbox.address());
+  JS::Rooted<JSObject*> sandbox(aCx);
+  aRv = xpc->CreateSandbox(aCx, aPrincipal, sandbox.address());
   if (NS_WARN_IF(aRv.Failed())) {
     return nullptr;
   }
 
-  nsCOMPtr<nsIGlobalObject> sandboxGlobalObject = xpc::NativeGlobal(aSandbox);
+  nsCOMPtr<nsIGlobalObject> sandboxGlobalObject = xpc::NativeGlobal(sandbox);
   if (!sandboxGlobalObject) {
     aRv.Throw(NS_ERROR_FAILURE);
     return nullptr;
@@ -666,7 +661,6 @@ private:
 
   RefPtr<ServiceWorkerRegistrationInfo> mRegistration;
   RefPtr<CompareCallback> mCallback;
-  JS::PersistentRooted<JSObject*> mSandbox;
   RefPtr<CacheStorage> mCacheStorage;
 
   nsTArray<RefPtr<CompareNetwork>> mCNList;
@@ -1286,8 +1280,7 @@ CompareManager::Initialize(nsIPrincipal* aPrincipal,
   AutoJSAPI jsapi;
   jsapi.Init();
   ErrorResult result;
-  mSandbox.init(jsapi.cx());
-  mCacheStorage = CreateCacheStorage(jsapi.cx(), aPrincipal, result, &mSandbox);
+  mCacheStorage = CreateCacheStorage(jsapi.cx(), aPrincipal, result);
   if (NS_WARN_IF(result.Failed())) {
     MOZ_ASSERT(!result.IsErrorWithMessage());
     return result.StealNSResult();
@@ -1429,8 +1422,7 @@ PurgeCache(nsIPrincipal* aPrincipal, const nsAString& aCacheName)
   AutoJSAPI jsapi;
   jsapi.Init();
   ErrorResult rv;
-  JS::Rooted<JSObject*> sandboxObject(jsapi.cx());
-  RefPtr<CacheStorage> cacheStorage = CreateCacheStorage(jsapi.cx(), aPrincipal, rv, &sandboxObject);
+  RefPtr<CacheStorage> cacheStorage = CreateCacheStorage(jsapi.cx(), aPrincipal, rv);
   if (NS_WARN_IF(rv.Failed())) {
     return rv.StealNSResult();
   }