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

chrome/browser/media/router/issue.cc

Index: chrome/browser/media/router/issue.cc
diff --git a/chrome/browser/media/router/issue.cc b/chrome/browser/media/router/issue.cc
index 6afa57e4c01cf2fe9bf2e6bb7be42b8709f6217d..0dd3488c63b7b60a9904e79744228d9aa5731bb2 100644
--- a/chrome/browser/media/router/issue.cc
+++ b/chrome/browser/media/router/issue.cc
@@ -20,7 +20,7 @@ Issue::Issue(const std::string& title,
              const MediaRoute::Id& route_id,
              const Issue::Severity severity,
              bool is_blocking,
-             const std::string& help_url)
+             int help_page_id)
     : title_(title),
       message_(message),
       default_action_(default_action),
@@ -29,7 +29,7 @@ Issue::Issue(const std::string& title,
       severity_(severity),
       id_(base::GenerateGUID()),
       is_blocking_(is_blocking),
-      help_url_(GURL(help_url)) {
+      help_page_id_(help_page_id) {
   DCHECK(!title_.empty());
   DCHECK(severity_ != FATAL || is_blocking_) << "Severity is " << severity_;