Don't register or use the DelegateExecute verb handler if it isn't present.

chrome/installer/util/browser_distribution.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.
 //
 // This file declares a class that contains various method related to branding.
 
 #ifndef CHROME_INSTALLER_UTIL_BROWSER_DISTRIBUTION_H_
 #define CHROME_INSTALLER_UTIL_BROWSER_DISTRIBUTION_H_
 #pragma once
 
@@ skipping 104 matching lines @@
   virtual int GetIconIndex();
 
   virtual bool GetChromeChannel(std::wstring* channel);
 
   // Returns true if the distribution includes a DelegateExecute verb handler,
   // and provides the COM registration data if so:
   // |handler_class_uuid| is the CommandExecuteImpl class UUID.
   // |type_lib_uuid| and |type_lib_version| identify its type library.
   // |interface_uuid| is the ICommandExecuteImpl interface UUID.
   // Only non-null parameters will be set, others will be ignored.
+  // Implementations that only provide a DelegateExecute handler for use on
+  // certain OS versions must only return true when run on those supported
+  // systems.
   virtual bool GetDelegateExecuteHandlerData(string16* handler_class_uuid,
                                              string16* type_lib_uuid,
                                              string16* type_lib_version,
                                              string16* interface_uuid);
 
   virtual void UpdateInstallStatus(bool system_install,
       installer::ArchiveType archive_type,
       installer::InstallStatus install_status);
 
   // Gets the experiment details for a given language-brand combo. If |flavor|
@@ skipping 27 matching lines @@
 
   const Type type_;
 
  private:
   BrowserDistribution();
 
   DISALLOW_COPY_AND_ASSIGN(BrowserDistribution);
 };
 
 #endif  // CHROME_INSTALLER_UTIL_BROWSER_DISTRIBUTION_H_