Refactor extension handling code from AppShimHost into ExtensionAppShimHandler.

apps/app_shim/app_shim_handler_mac.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 APPS_APP_SHIM_APP_SHIM_HANDLER_MAC_H_
 #define APPS_APP_SHIM_APP_SHIM_HANDLER_MAC_H_
 
 #include <string>
 
+class Profile;
+
 namespace apps {
 
 // Registrar, and interface for services that can handle interactions with OSX
 // shim processes.
 class AppShimHandler {
  public:
   class Host {
    public:
     // Invoked when the app is closed in the browser process.
     virtual void OnAppClosed() = 0;
 
+    // Allows the handler to determine which app this host corresponds to.
+    virtual Profile* GetProfile() const = 0;
+    virtual std::string GetAppId() const = 0;
+
    protected:
     virtual ~Host() {}
   };
 
   // Register a handler for an |app_mode_id|.
   static void RegisterHandler(const std::string& app_mode_id,
                               AppShimHandler* handler);
 
   // Remove a handler for an |app_mode_id|.
   static void RemoveHandler(const std::string& app_mode_id);
 
-  // Returns the handler registered for the given |app_mode_id|, or NULL if none
-  // is registered.
+  // Returns the handler registered for the given |app_mode_id|. If there is
+  // none registered, it returns the default handler or NULL if there is no
+  // default handler.
   static AppShimHandler* GetForAppMode(const std::string& app_mode_id);
 
+  // Sets the default handler to return when there is no app-specific handler.
+  // Setting this to NULL removes the default handler.
+  static void SetDefaultHandler(AppShimHandler* handler);
+
   // Invoked by the shim host when the shim process is launched. The handler
   // must return true if successful, or false to indicate back to the shim
   // process that it should close.
   virtual bool OnShimLaunch(Host* host) = 0;
 
   // Invoked by the shim host when the connection to the shim process is closed.
   virtual void OnShimClose(Host* host) = 0;
 
   // Invoked by the shim host when the shim process receives a focus event.
   virtual void OnShimFocus(Host* host) = 0;
 
  protected:
   AppShimHandler() {}
   virtual ~AppShimHandler() {}
 };
 
 }  // namespace apps
 
 #endif  // APPS_APP_SHIM_APP_SHIM_HANDLER_MAC_H_