Fix flaky WindowsApiSetIcon test.

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

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "apps/app_window.h"
 #include "apps/app_window_registry.h"
 #include "apps/ui/native_app_window.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "chrome/browser/apps/app_browsertest_util.h"
@@ skipping 33 matching lines @@
 };
 
 }  // namespace
 
 namespace extensions {
 
 // Tests chrome.app.window.setIcon.
 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.
   while (test_observer->icon_updates() < 1) {
     base::RunLoop run_loop;
     run_loop.RunUntilIdle();
   }
   AppWindow* app_window = GetFirstAppWindow();
   ASSERT_TRUE(app_window);
   EXPECT_NE(std::string::npos,
@@ skipping 33 matching lines @@
   EXPECT_TRUE(RunPlatformAppTest(
       "platform_apps/windows_api_always_on_top/no_permissions")) << message_;
 }
 
 IN_PROC_BROWSER_TEST_F(PlatformAppBrowserTest, WindowsApiGet) {
   EXPECT_TRUE(RunPlatformAppTest("platform_apps/windows_api_get"))
       << message_;
 }
 
 }  // namespace extensions