Make sure that Content Handled application can be connected multiple times.

mojo/application_manager/application_loader.h

 // Copyright 2014 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 MOJO_APPLICATION_MANAGER_APPLICATION_LOADER_H_
 #define MOJO_APPLICATION_MANAGER_APPLICATION_LOADER_H_
 
-#include "base/memory/ref_counted.h"
+#include "base/callback.h"
 #include "mojo/application_manager/application_manager_export.h"
 #include "mojo/public/cpp/system/core.h"
 #include "mojo/services/public/interfaces/network/url_loader.mojom.h"
 #include "url/gurl.h"
 
 namespace mojo {
 
 class ApplicationManager;
 
 // Interface to allowing loading behavior to be established for schemes,
 // specific urls or as the default.
 // A ApplicationLoader is responsible to using whatever mechanism is appropriate
 // to load the application at url.
 // The handle to the shell is passed to that application so it can bind it to
 // a Shell instance. This will give the Application a way to connect to other
 // apps and services.
 class MOJO_APPLICATION_MANAGER_EXPORT ApplicationLoader {
  public:
-  class MOJO_APPLICATION_MANAGER_EXPORT LoadCallbacks
-      : public base::RefCounted<LoadCallbacks> {
-   public:
-    // Register the requested application with ApplicationManager. If the
-    // returned handle is valid, it should be used to implement the
-    // mojo::Application interface.
-    virtual ScopedMessagePipeHandle RegisterApplication() = 0;
+  typedef base::Callback<
+      void(const GURL&, ScopedMessagePipeHandle, URLResponsePtr)> LoadCallback;
+  virtual ~ApplicationLoader() {}
 
-    // Load the requested application with a content handler.
-    virtual void LoadWithContentHandler(const GURL& content_handler_url,
-                                        URLResponsePtr url_response) = 0;
-
-   protected:
-    friend base::RefCounted<LoadCallbacks>;
-    virtual ~LoadCallbacks() {}
-  };
-
-  // Implements RegisterApplication() by returning a handle that was specified
-  // at construction time. LoadWithContentHandler() is not supported.
-  class MOJO_APPLICATION_MANAGER_EXPORT SimpleLoadCallbacks
-      : public LoadCallbacks {
-   public:
-    SimpleLoadCallbacks(ScopedMessagePipeHandle shell_handle);
-    ScopedMessagePipeHandle RegisterApplication() override;
-    void LoadWithContentHandler(const GURL& content_handler_url,
-                                URLResponsePtr response) override;
-
-   private:
-    ScopedMessagePipeHandle shell_handle_;
-    ~SimpleLoadCallbacks() override;
-  };
-
-  virtual ~ApplicationLoader() {}
+  // Returns a callback that will should never be called.
+  static LoadCallback SimpleLoadCallback();
 
   // Load the application named |url|. Applications can be loaded two ways:
   //
-  // 1. |url| can refer directly to a Mojo application. In this case, call
-  //    callbacks->RegisterApplication(). The returned handle should be used to
-  //    implement the mojo.Application interface. Note that the returned handle
-  //    can be invalid in the case where the application has already been
-  //    loaded.
+  // 1. |url| can refer directly to a Mojo application. In this case,
+  //    shell_handle should be used to implement the mojo.Application interface.
   //
   // 2. |url| can refer to some content that can be handled by some other Mojo
-  //    application. In this case, call callbacks->LoadWithContentHandler() and
-  //    specify the URL of the application that should handle the content.
-  //    The specified application must implement the mojo.ContentHandler
-  //    interface.
+  //    application. In this case, call callbacks and specify the URL of the
+  //    application that should handle the content.  The specified application
+  //    must implement the mojo.ContentHandler interface.
   virtual void Load(ApplicationManager* application_manager,
                     const GURL& url,
-                    scoped_refptr<LoadCallbacks> callbacks) = 0;
+                    ScopedMessagePipeHandle shell_handle,
+                    LoadCallback callback) = 0;
 
   // Called when the Application exits.
   virtual void OnApplicationError(ApplicationManager* manager,
                                   const GURL& url) = 0;
 
  protected:
   ApplicationLoader() {}
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_APPLICATION_MANAGER_APPLICATION_LOADER_H_