Bug 1378171 - add a test preventing us from loading scripts unintentionally during content process startup, r=mconley.

browser/base/content/test/performance/browser.ini

@@ -3,6 +3,8 @@ support-files =
   head.js
 [browser_appmenu_reflows.js]
 [browser_startup.js]
+[browser_startup_content.js]
+skip-if = !e10s
 [browser_startup_images.js]
 skip-if = !debug
 [browser_tabclose_grow_reflows.js]

browser/base/content/test/performance/browser_startup_content.js

@@ -0,0 +1,81 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* This test records which services, JS components and JS modules are loaded
+ * when creating a new content process.
+ *
+ * If you made changes that cause this test to fail, it's likely because you
+ * are loading more JS code during content process startup.
+ *
+ * If your code isn't strictly required to show a page, consider loading it
+ * lazily. If you can't, consider delaying its load until after we have started
+ * handling user events.
+ */
+
+"use strict";
+
+const blacklist = {
+  components: new Set([
+    "PushComponents.js",
+    "TelemetryStartup.js",
+  ]),
+  modules: new Set([
+    "resource:///modules/ContentWebRTC.jsm",
+    "resource://gre/modules/InlineSpellChecker.jsm",
+    "resource://gre/modules/InlineSpellCheckerContent.jsm",
+    "resource://gre/modules/Promise.jsm",
+    "resource://gre/modules/Task.jsm",
+    "resource://gre/modules/debug.js",
+    "resource://gre/modules/osfile.jsm",
+  ]),
+  services: new Set([
+    "@mozilla.org/base/telemetry-startup;1",
+    "@mozilla.org/push/Service;1",
+  ])
+};
+
+add_task(async function() {
+  SimpleTest.requestCompleteLog();
+
+  let tab = await BrowserTestUtils.openNewForegroundTab({gBrowser,
+                                                         forceNewProcess: true});
+
+  let mm = gBrowser.selectedBrowser.messageManager;
+  let promise = BrowserTestUtils.waitForMessage(mm, "Test:LoadedScripts");
+
+  // Load a custom frame script to avoid using ContentTask which loads Task.jsm
+  mm.loadFrameScript("data:text/javascript,(" + function() {
+    /* eslint-env mozilla/frame-script */
+    const {classes: Cc, interfaces: Ci, manager: Cm} = Components;
+    Cm.QueryInterface(Ci.nsIServiceManager);
+
+    let loader = Cc["@mozilla.org/moz/jsloader;1"].getService(Ci.xpcIJSModuleLoader);
+    sendAsyncMessage("Test:LoadedScripts", {
+      /* Keep only the file name for components, as the path is an absolute file
+         URL rather than a resource:// URL like for modules. */
+      components: loader.loadedComponents().map(f => f.replace(/.*\//, "")),
+      modules: loader.loadedModules(),
+      services: Object.keys(Cc).filter(c => {
+        try {
+          Cm.isServiceInstantiatedByContractID(c, Ci.nsISupports);
+          return true;
+        } catch (e) {
+          return false;
+        }
+      })
+    });
+  } + ")()", false);
+
+  let loadedList = await promise;
+  for (let scriptType in blacklist) {
+    info(scriptType);
+    for (let file of blacklist[scriptType]) {
+      ok(!loadedList[scriptType].includes(file), `${file} is not allowed`);
+    }
+    for (let file of loadedList[scriptType]) {
+      info(file);
+    }
+  }
+
+  await BrowserTestUtils.removeTab(tab);
+});

testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm

@@ -910,7 +910,7 @@ this.BrowserTestUtils = {
       messageManager.addMessageListener(message, function onMessage(msg) {
         if (!checkFn || checkFn(msg)) {
           messageManager.removeMessageListener(message, onMessage);
-          resolve();
+          resolve(msg.data);
         }
       });
     });