Make application shortcuts point to app_host.exe, install App Host during app installation.

chrome/browser/extensions/unpacked_installer.h

 // Copyright (c) 2012 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_EXTENSIONS_UNPACKED_INSTALLER_H_
 #define CHROME_BROWSER_EXTENSIONS_UNPACKED_INSTALLER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 52 matching lines @@
 
   // Must be called from the UI thread.
   void CheckRequirements();
 
   // Callback from RequirementsChecker.
   void OnRequirementsChecked(std::vector<std::string> requirement_errors);
 
   // Verifies if loading unpacked extensions is allowed.
   bool IsLoadingUnpackedAllowed() const;
 
-  // We change the input extension path to an absolute path, on the file thread.
+  // We change the input extension path to an absolute path, on the FILE thread.
   // Then we need to check the file access preference, which needs
   // to happen back on the UI thread, so it posts CheckExtensionFileAccess on
   // the UI thread. In turn, once that gets the pref, it goes back to the
-  // file thread with LoadWithFileAccess.
+  // FILE thread with LoadWithFileAccess.
   // TODO(yoz): It would be nice to remove this ping-pong, but we need to know
   // what file access flags to pass to extension_file_util::LoadExtension.
   void GetAbsolutePath();
   void CheckExtensionFileAccess();
   void LoadWithFileAccess(int flags);
 
   // Notify the frontend that there was an error loading an extension.
   void ReportExtensionLoadError(const std::string& error);
 
   // Called when an unpacked extension has been loaded and installed.
   void OnLoaded();
 
+  // Runs on UI thread. If App Host is not installed, calls installer and
+  // posts OnAppHostInstallationComplete() as call back.  Else proceeds to
+  // CompleteInstall().
+  void BeginInstall();
+
+  // Runs on UI thread. Callback function for AppHostInstaller.
+  // If not |success|, shows error message. Else proceeds to CompleteInstall().
+  void OnAppHostInstallation(bool success);
+
+  // Runs on UI thread. Installs the unpacked extension into the profile and
+  // notifies the frontend.
+  void CompleteInstall();
+
   // Helper to get the Extension::CreateFlags for the installing extension.
   int GetFlags();
 
   base::WeakPtr<ExtensionService> service_weak_;
 
   // The pathname of the directory to load from, which is an absolute path
   // after GetAbsolutePath has been called.
   FilePath extension_path_;
 
   // If true and the extension contains plugins, we prompt the user before
   // loading.
   bool prompt_for_plugins_;
 
   scoped_ptr<RequirementsChecker> requirements_checker_;
 
   scoped_refptr<const Extension> extension_;
 
   // Whether to require the extension installed to have a modern manifest
   // version.
   bool require_modern_manifest_version_;
 
   DISALLOW_COPY_AND_ASSIGN(UnpackedInstaller);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_UNPACKED_INSTALLER_H_