[Media Router] Consistently refer to issue's learn more help page by ID.

chrome/browser/media/router/issue.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 CHROME_BROWSER_MEDIA_ROUTER_ISSUE_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_ISSUE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 32 matching lines @@
   // Creates a custom issue.
   // |title|: The title for the issue.
   // |message|: The optional description message for the issue.
   // |default_action|: Default action user can take to resolve the issue.
   // |secondary_actions|: Array of options user can take to resolve the
   //                      issue. Can be empty. Currently only one secondary
   //                      action is supported.
   // |route_id|: The route id, or empty if global.
   // |severity|: The severity of the issue.
   // |is_blocking|: True if the issue needs to be resolved before continuing.
-  // |help_url|: Required if one of the actions is learn-more.
+  // |help_page_id|: Required if one of the actions is learn-more. Passes in -1
+  //                 if the issue is not associated with a help page.
   Issue(const std::string& title,
         const std::string& message,
         const IssueAction& default_action,
         const std::vector<IssueAction>& secondary_actions,
         const MediaRoute::Id& route_id,
         const Severity severity,
         bool is_blocking,
-        const std::string& helpUrl);
+        int help_page_id);
 
   Issue(const Issue& other);
 
   ~Issue();
 
   // See constructor comments for more information about these fields.
   const std::string& title() const { return title_; }
   const std::string& message() const { return message_; }
   IssueAction default_action() const { return default_action_; }
   const std::vector<IssueAction>& secondary_actions() const {
     return secondary_actions_;
   }
   MediaRoute::Id route_id() const { return route_id_; }
   Severity severity() const { return severity_; }
   const Issue::Id& id() const { return id_; }
   bool is_blocking() const { return is_blocking_; }
   bool is_global() const { return route_id_.empty(); }
-  const GURL& help_url() const { return help_url_; }
+  int help_page_id() const { return help_page_id_; }
 
   bool Equals(const Issue& other) const;
 
  private:
   std::string title_;
   std::string message_;
   IssueAction default_action_;
   std::vector<IssueAction> secondary_actions_;
   std::string route_id_;
   Severity severity_;
   Issue::Id id_;
   bool is_blocking_;
-  GURL help_url_;
+  int help_page_id_;
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_ISSUE_H_