Bug 851516: browser-chrome should wait for delayedStartup. r=joe

--HG--
extra : rebase_source : 242defb996e64271c100b7de1140dde76d3e3c39

browser/base/content/browser.js

@@ -1640,6 +1640,7 @@ var gBrowserInit = {
     }
 
     Services.obs.notifyObservers(window, "browser-delayed-startup-finished", "");
+    setTimeout(function () { BrowserChromeTest.markAsReady(); }, 0);
     TelemetryTimestamps.add("delayedStartupFinished");
   },
 
@@ -7537,3 +7538,20 @@ function focusNextFrame(event) {
     focusAndSelectUrlBar();
 }
 
+let BrowserChromeTest = {
+  _cb: null,
+  _ready: false,
+  markAsReady: function () {
+    this._ready = true;
+    if (this._cb) {
+      this._cb();
+      this._cb = null;
+    }
+  },
+  runWhenReady: function (cb) {
+    if (this._ready)
+      cb();
+    else
+      this._cb = cb;
+  }
+};

testing/mochitest/browser-test.js

@@ -92,6 +92,15 @@ Tester.prototype = {
   },
 
   start: function Tester_start() {
+    // Check whether this window is ready to run tests.
+    if (window.BrowserChromeTest) {
+      BrowserChromeTest.runWhenReady(this.actuallyStart.bind(this));
+      return;
+    }
+    this.actuallyStart();
+  },
+
+  actuallyStart: function Tester_actuallyStart() {
     //if testOnLoad was not called, then gConfig is not defined
     if (!gConfig)
       gConfig = readConfig();