Introduce AppsClient and use it in apps to get the loaded profiles list.

chrome/browser/apps/chrome_apps_client.h

+// Copyright 2013 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_APPS_CHROME_APPS_CLIENT_H_
+#define CHROME_BROWSER_APPS_CHROME_APPS_CLIENT_H_
+
+#include "apps/apps_client.h"
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+
+template<typename T> struct DefaultSingletonTraits;
+
+// The implementation of AppsClient for Chrome.
+class ChromeAppsClient : public apps::AppsClient {
+ public:
+  ChromeAppsClient();
+  virtual ~ChromeAppsClient();
+
+  // Get the LazyInstance for ChromeAppsClient.
+  static ChromeAppsClient* GetInstance();
+
+ private:
+  friend struct DefaultSingletonTraits<ChromeAppsClient>;
+
+  // apps::AppsClient
+  virtual std::vector<content::BrowserContext*> GetLoadedBrowserContexts()
+      OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeAppsClient);
+};
+
+#endif  // CHROME_BROWSER_APPS_CHROME_APPS_CLIENT_H_