mash: Update shelf pin prefs in ShelfModelObserver overrides.

chrome/browser/ui/ash/launcher/launcher_app_updater.h

 // Copyright 2016 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_ASH_LAUNCHER_LAUNCHER_APP_UPDATER_H_
 #define CHROME_BROWSER_UI_ASH_LAUNCHER_LAUNCHER_APP_UPDATER_H_
 
 #include <string>
 
 #include "base/macros.h"
 
 namespace content {
 class BrowserContext;
 }
 
 // Responsible for handling of Chrome app life-cycle events.
 class LauncherAppUpdater {

[James Cook, 2017/03/29 14:28:02]

Aside: This class is weird. It seems to exist mostly to be a delegate interface,
but I don't understand why the delegation happens. All the code is in
chrome/browser/ui.

[msw, 2017/03/29 21:34:17]

I suppose it's because c/b/ui/app_list can't depend on c/b/ui/ash/launcher.
(Chrome's handling of extensions vs arc apps shouldn't be known to app_list?)

  public:
   class Delegate {
    public:
     virtual void OnAppInstalled(content::BrowserContext* browser_context,
                                 const std::string& app_id) {}
     virtual void OnAppUpdated(content::BrowserContext* browser_context,
                               const std::string& app_id) {}
     virtual void OnAppUninstalledPrepared(
         content::BrowserContext* browser_context,
         const std::string& app_id) {}
     virtual void OnAppUninstalled(content::BrowserContext* browser_context,
                                   const std::string& app_id) {}
 
+    // This pair of functions is called before and after disabling an app. This
+    // prevents shelf item removal from triggering a sync model pref update.
+    virtual void OnAppDisabling(const std::string& app_id) {}
+    virtual void OnAppDisabled(const std::string& app_id) {}
+
    protected:
     virtual ~Delegate() {}
   };
 
   virtual ~LauncherAppUpdater();
 
   Delegate* delegate() { return delegate_; }
 
   content::BrowserContext* browser_context() { return browser_context_; }
 
  protected:
   LauncherAppUpdater(Delegate* delegate,
                      content::BrowserContext* browser_context);
 
  private:
   // Unowned pointers
   Delegate* delegate_;
   content::BrowserContext* browser_context_;
 
   DISALLOW_COPY_AND_ASSIGN(LauncherAppUpdater);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_LAUNCHER_LAUNCHER_APP_UPDATER_H_