Implement Windows GPO support for "dlpref" in component updater.

components/update_client/configurator.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 COMPONENTS_UPDATE_CLIENT_CONFIGURATOR_H_
 #define COMPONENTS_UPDATE_CLIENT_CONFIGURATOR_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 59 matching lines @@
   virtual std::string GetLang() const = 0;
 
   // Returns the OS's long name like "Windows", "Mac OS X", etc.
   virtual std::string GetOSLongName() const = 0;
 
   // Parameters added to each url request. It can be empty if none are needed.
   // The return string must be safe for insertion as an attribute in an
   // XML element.
   virtual std::string ExtraRequestParams() const = 0;
 
+  // Provides a hint for the server to control the order in which multiple
+  // download urls are returned. The hint may or may not be honored in the
+  // response returned by the server.
+  // Returns an empty string if no policy is in effect.
+  virtual std::string GetDownloadPreference() const = 0;
+
   // The source of contexts for all the url requests.
   virtual net::URLRequestContextGetter* RequestContext() const = 0;
 
   // Returns a new out of process patcher. May be NULL for implementations
   // that patch in-process.
   virtual scoped_refptr<update_client::OutOfProcessPatcher>
   CreateOutOfProcessPatcher() const = 0;
 
   // True means that this client can handle delta updates.
   virtual bool DeltasEnabled() const = 0;
 
   // True means that the background downloader can be used for downloading
   // non on-demand components.
   virtual bool UseBackgroundDownloader() const = 0;
 
   // Gets a task runner to a blocking pool of threads suitable for worker jobs.
   virtual scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner()
       const = 0;
 
  protected:
   friend class base::RefCountedThreadSafe<Configurator>;
 
   virtual ~Configurator() {}
 };
 
 }  // namespace update_client
 
 #endif  // COMPONENTS_UPDATE_CLIENT_CONFIGURATOR_H_