Fix flaky WindowsApiSetIcon test.

BUG=396466

Review URL: https://codereview.chromium.org/411253002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285545 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/extensions/api/app_window/app_window_apitest.cc

@@ -51,8 +51,13 @@ namespace extensions {
 IN_PROC_BROWSER_TEST_F(ExperimentalPlatformAppBrowserTest, WindowsApiSetIcon) {
   scoped_ptr<TestAppWindowRegistryObserver> test_observer(
       new TestAppWindowRegistryObserver(browser()->profile()));
-  LoadAndLaunchPlatformApp("windows_api_set_icon", "IconSet");
+  ExtensionTestMessageListener listener("ready", true);
+
+  // Launch the app and wait for it to be ready.
+  LoadAndLaunchPlatformApp("windows_api_set_icon", &listener);
   EXPECT_EQ(0, test_observer->icon_updates());
+  listener.Reply("");
+
   // Now wait until the WebContent has decoded the icon and chrome has
   // processed it. This needs to be in a loop since the renderer runs in a
   // different process.

chrome/test/data/extensions/platform_apps/windows_api_set_icon/background.js

@@ -3,9 +3,9 @@
 // found in the LICENSE file.
 
 chrome.app.runtime.onLaunched.addListener(function() {
-  chrome.test.sendMessage("Launched");
   chrome.app.window.create('test.html', {}, function(win) {
-    win.setIcon("icon.png");
-    chrome.test.sendMessage('IconSet');
+    chrome.test.sendMessage('ready', function() {
+      win.setIcon("icon.png");
+    });
   });
 });