add minimal prerequisites for previous commit

dom/workers/ScriptLoader.cpp

@@ -853,12 +853,31 @@ private:
 
     NS_ASSERTION(aString, "This should never be null!");
 
-    // Make sure we're not seeing the result of a 404 or something by checking
-    // the 'requestSucceeded' attribute on the http channel.
     nsCOMPtr<nsIRequest> request;
     nsresult rv = aLoader->GetRequest(getter_AddRefs(request));
     NS_ENSURE_SUCCESS(rv, rv);
 
+    nsCOMPtr<nsIChannel> channel = do_QueryInterface(request);
+    MOZ_ASSERT(channel);
+
+    nsIScriptSecurityManager* ssm = nsContentUtils::GetSecurityManager();
+    NS_ASSERTION(ssm, "Should never be null!");
+
+    nsCOMPtr<nsIPrincipal> channelPrincipal;
+    rv = ssm->GetChannelResultPrincipal(channel, getter_AddRefs(channelPrincipal));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    nsIPrincipal* principal = mWorkerPrivate->GetPrincipal();
+    if (!principal) {
+      WorkerPrivate* parentWorker = mWorkerPrivate->GetParent();
+      MOZ_ASSERT(parentWorker, "Must have a parent!");
+      principal = parentWorker->GetPrincipal();
+    }
+
+    // Make sure we're not seeing the result of a 404 or something by checking
+    // the 'requestSucceeded' attribute on the http channel.
     nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(request);
     if (httpChannel) {
       bool requestSucceeded;
@@ -894,9 +913,6 @@ private:
       return NS_ERROR_FAILURE;
     }
 
-    nsCOMPtr<nsIChannel> channel = do_QueryInterface(request);
-    NS_ASSERTION(channel, "This should never fail!");
-
     // Figure out what we actually loaded.
     nsCOMPtr<nsIURI> finalURI;
     rv = NS_GetFinalChannelURI(channel, getter_AddRefs(finalURI));