Bug 827976 - Test that the hidden window is not loaded before first paint. r=florian

Differential Revision: https://phabricator.services.mozilla.com/D21087

--HG--
extra : moz-landing-system : lando

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

@@ -23,6 +23,8 @@ skip-if = !debug
 [browser_startup.js]
 [browser_startup_content.js]
 skip-if = !e10s
+[browser_startup_hiddenwindow.js]
+skip-if = os == 'mac'
 [browser_startup_flicker.js]
 run-if = debug || devedition || nightly_build # Requires startupRecorder.js, which isn't shipped everywhere by default
 [browser_tabclose_grow.js]

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

@@ -0,0 +1,38 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function() {
+  if (!AppConstants.NIGHTLY_BUILD && !AppConstants.MOZ_DEV_EDITION && !AppConstants.DEBUG) {
+    ok(!("@mozilla.org/test/startuprecorder;1" in Cc),
+       "the startup recorder component shouldn't exist in this non-nightly/non-devedition/" +
+       "non-debug build.");
+    return;
+  }
+
+  let startupRecorder = Cc["@mozilla.org/test/startuprecorder;1"].getService().wrappedJSObject;
+  await startupRecorder.done;
+
+  let extras = Cu.cloneInto(startupRecorder.data.extras, {});
+
+  let phasesExpectations = {
+    "before profile selection": false,
+    "before opening first browser window": false,
+    "before first paint": !Services.prefs.getBoolPref("toolkit.lazyHiddenWindow"),
+
+    // Bug 1531854
+    "before handling user events": true,
+    "before becoming idle": true,
+  };
+
+  for (let phase in extras) {
+    if (!(phase in phasesExpectations)) {
+      ok(false, `Startup phase '${phase}' should be specified.`);
+      continue;
+    }
+
+    is(extras[phase].hiddenWindowLoaded, phasesExpectations[phase],
+       `Hidden window loaded at '${phase}': ${phasesExpectations[phase]}`);
+  }
+});

browser/components/tests/startupRecorder.js

@@ -49,6 +49,7 @@ function startupRecorder() {
       "image-loading": new Set(),
     },
     code: {},
+    extras: {},
     prefStats: {},
   };
   this.done = new Promise(resolve => { this._resolve = resolve; });
@@ -73,6 +74,9 @@ startupRecorder.prototype = {
         }
       }),
     };
+    this.data.extras[name] = {
+      hiddenWindowLoaded: Services.appShell.hasHiddenWindow,
+    };
   },
 
   observe(subject, topic, data) {