Handle app custom icon via aura::Window property.

chrome/browser/ui/test/test_app_window_observer.h

+// Copyright 2017 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.
+
+#ifndef CHROME_BROWSER_UI_TEST_TEST_APP_WINDOW_OBSERVER_H_
+#define CHROME_BROWSER_UI_TEST_TEST_APP_WINDOW_OBSERVER_H_
+
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "extensions/browser/app_window/app_window_registry.h"
+#include "ui/aura/window_observer.h"
+
+namespace content {
+class BrowserContext;
+}
+
+class TestAppWindowObserver : public extensions::AppWindowRegistry::Observer,
+                              public aura::WindowObserver {
+ public:
+  explicit TestAppWindowObserver(content::BrowserContext* context);
+  ~TestAppWindowObserver() override;
+
+  // Waits for one icon update.
+  void WaitForIconUpdate();
+  // Waits for |updates| number of icon updates.
+  void WaitForIconUpdates(int updates);
+
+  int icon_updates() const { return icon_updates_; }
+
+ private:
+  // AppWindowRegistry::Observer:
+  void OnAppWindowAdded(extensions::AppWindow* app_window) override;
+  void OnAppWindowRemoved(extensions::AppWindow* app_window) override;
+
+  // aura::WindowObserver:
+  void OnWindowPropertyChanged(aura::Window* window,
+                               const void* key,
+                               intptr_t old) override;
+  content::BrowserContext* const context_;
+  int icon_updates_ = 0;
+  int expeced_icon_updates_ = 0;

[Devlin, 2017/05/31 22:00:01]

typo: expected

[khmel, 2017/06/01 16:56:52]

Done.

+  std::vector<aura::Window*> windows_;
+  base::OnceClosure icon_updated_callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestAppWindowObserver);
+};
+
+#endif  // CHROME_BROWSER_UI_TEST_TEST_APP_WINDOW_OBSERVER_H_