Extract shell methods from ApplicationImpl into a base class, and pass this to Initialize() instead.

components/filesystem/file_system_app.h

 // Copyright 2015 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 COMPONENTS_FILESYSTEM_FILE_SYSTEM_APP_H_
 #define COMPONENTS_FILESYSTEM_FILE_SYSTEM_APP_H_
 
 #include "base/macros.h"
 #include "components/filesystem/directory_impl.h"
 #include "components/filesystem/file_system_impl.h"
 #include "components/filesystem/public/interfaces/file_system.mojom.h"
 #include "mojo/services/tracing/public/cpp/tracing_impl.h"
 #include "mojo/shell/public/cpp/application_delegate.h"
 #include "mojo/shell/public/cpp/interface_factory.h"
 
 namespace mojo {
-class ApplicationImpl;
+class Shell;
 }
 
 namespace filesystem {
 
 class FileSystemApp : public mojo::ApplicationDelegate,
                       public mojo::InterfaceFactory<FileSystem> {
  public:
   FileSystemApp();
   ~FileSystemApp() override;
 
   // Called by individual FileSystem objects to register lifetime events.
   void RegisterDirectoryToClient(DirectoryImpl* directory,
                                  FileSystemClientPtr client);
 
  private:
   // We set the DirectoryImpl's error handler to this function. We do this so
   // that we can QuitNow() once the last DirectoryImpl has closed itself.
   void OnDirectoryConnectionError(DirectoryImpl* directory);
 
   // |ApplicationDelegate| override:
-  void Initialize(mojo::ApplicationImpl* app) override;
+  void Initialize(mojo::Shell* shell, const std::string& url,
+                  uint32_t id) override;
   bool AcceptConnection(
       mojo::ApplicationConnection* connection) override;
   bool ShellConnectionLost() override;
 
   // |InterfaceFactory<Files>| implementation:
   void Create(mojo::ApplicationConnection* connection,
               mojo::InterfaceRequest<FileSystem> request) override;
 
   // Use a vector to work around map not letting us use FileSystemClientPtr as
   // a value in a std::map. The move constructors are to allow us to deal with
   // FileSystemClientPtr inside a vector.
   struct Client {
     Client(DirectoryImpl* directory, FileSystemClientPtr fs_client);
     Client(Client&& rhs);
     ~Client();
 
     Client& operator=(Client&& rhs);
 
     DirectoryImpl* directory_;
     FileSystemClientPtr fs_client_;
   };
   std::vector<Client> client_mapping_;
 
-  mojo::ApplicationImpl* app_;
+  mojo::Shell* shell_;
   mojo::TracingImpl tracing_;
 
   // Set to true when our shell connection is closed. On connection error, we
   // then broadcast a notification to all FileSystemClients that they should
   // shut down. Once the final one does, then we QuitNow().
   bool in_shutdown_;
 
   DISALLOW_COPY_AND_ASSIGN(FileSystemApp);
 };
 
 }  // namespace filesystem
 
 #endif  // COMPONENTS_FILESYSTEM_FILE_SYSTEM_APP_H_