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"
+#include "base/lazy_instance.h"

[tapted, 2013/09/04 01:08:35]

I think you can forward declare this, with 

template <typename T> struct DefaultLazyInstanceTraits;

This would match the guide in singleton.h. Someone has probably just been uhhh
lazy updating lazy_instance.h.

But would this be better as a Singleton anyway? LazyInstance is needed if you
need multiple instances of the same type, but this is bound to a single instance
for the type ChromeAppsClient.

[benwells, 2013/09/10 16:48:50]

Done.

+
+// The implementation of AppsClient for Chrome.
+class ChromeAppsClient : public apps::AppsClient {
+ public:
+  ChromeAppsClient();
+  virtual ~ChromeAppsClient();
+
+  // apps::AppsClient
+  virtual std::vector<content::BrowserContext*> GetLoadedBrowserContexts()

[tapted, 2013/09/04 01:08:35]

nit: overrides after newly introduced functions? I think it applies for static
fns too.

[benwells, 2013/09/10 16:48:50]

Actually it should be private. Moved to private.

+      OVERRIDE;
+
+  // Get the LazyInstance for ChromeAppsClient.
+  static ChromeAppsClient* GetInstance();
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<ChromeAppsClient>;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeAppsClient);
+};
+
+#endif  // CHROME_BROWSER_APPS_CHROME_APPS_CLIENT_H_