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

chrome/browser/media/router/mojo/media_router_mojo_impl_unittest.cc

 // 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.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <utility>
@@ skipping 84 matching lines @@
 interfaces::IssuePtr CreateMojoIssue(const std::string& title) {
   interfaces::IssuePtr mojoIssue = interfaces::Issue::New();
   mojoIssue->title = title;
   mojoIssue->message = "msg";
   mojoIssue->route_id = "";
   mojoIssue->default_action = interfaces::Issue::ActionType::DISMISS;
   mojoIssue->secondary_actions =
       mojo::Array<interfaces::Issue::ActionType>::New(0);
   mojoIssue->severity = interfaces::Issue::Severity::WARNING;
   mojoIssue->is_blocking = false;
-  mojoIssue->help_url = "";
+  mojoIssue->help_page_id = -1;
   return mojoIssue;
 }
 
 interfaces::MediaRoutePtr CreateMojoRoute() {
   interfaces::MediaRoutePtr route = interfaces::MediaRoute::New();
   route->media_source = kSource;
   route->media_sink_id = kSinkId;
   route->media_route_id = kRouteId;
   route->description = kDescription;
   route->is_local = true;
@@ skipping 1516 matching lines @@
   EXPECT_CALL(mock_media_route_provider_,
               UpdateMediaSinks(mojo::String(MediaSourceForDesktop().id())))
       .WillOnce(InvokeWithoutArgs([&run_loop2]() {
         run_loop2.Quit();
       }));
 
   run_loop2.Run();
 }
 
 }  // namespace media_router