Don't return installed apps in webstore searches in Launcher

chrome/browser/ui/app_list/app_list_controller_delegate.h

 // Copyright 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_UI_APP_LIST_APP_LIST_CONTROLLER_DELEGATE_H_
 #define CHROME_BROWSER_UI_APP_LIST_APP_LIST_CONTROLLER_DELEGATE_H_
 
 #include <string>
 
 #include "chrome/common/extensions/extension_constants.h"
@@ skipping 141 matching lines @@
   // The launch type specifies whether a hosted app should launch as a separate
   // window, fullscreened or as a tab.
   extensions::LaunchType GetExtensionLaunchType(
       Profile* profile, const std::string& app_id);
   virtual void SetExtensionLaunchType(
       Profile* profile,
       const std::string& extension_id,
       extensions::LaunchType launch_type);
 
   // Returns true if the given extension is installed.
-  bool IsExtensionInstalled(Profile* profile, const std::string& app_id);
+  virtual bool IsExtensionInstalled(Profile* profile,
+                                    const std::string& app_id);
 
   extensions::InstallTracker* GetInstallTrackerFor(Profile* profile);
 
   // Get the list of installed apps for the given profile.
   void GetApps(Profile* profile, extensions::ExtensionSet* out_apps);
 
   // Called when a search is started using the app list search box.
   void OnSearchStarted();
 };
 
 #endif  // CHROME_BROWSER_UI_APP_LIST_APP_LIST_CONTROLLER_DELEGATE_H_