[Media Router] Clean up issues related code.

chrome/browser/ui/toolbar/media_router_action.h

Index: chrome/browser/ui/toolbar/media_router_action.h
diff --git a/chrome/browser/ui/toolbar/media_router_action.h b/chrome/browser/ui/toolbar/media_router_action.h
index 676a1f68b98eeb972d74e15cf5c2cb7bb8511866..16db2f548267f3c4e25128ee7bb42352896317c6 100644
--- a/chrome/browser/ui/toolbar/media_router_action.h
+++ b/chrome/browser/ui/toolbar/media_router_action.h
@@ -9,6 +9,7 @@
 #include <string>
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "base/scoped_observer.h"
 #include "chrome/browser/media/router/issues_observer.h"
 #include "chrome/browser/media/router/media_routes_observer.h"
@@ -61,7 +62,8 @@ class MediaRouterAction : public ToolbarActionViewController,
   bool DisabledClickOpensMenu() const override;
 
   // media_router::IssuesObserver:
-  void OnIssueUpdated(const media_router::Issue* issue) override;
+  void OnIssue(const media_router::Issue& issue) override;
+  void OnIssuesCleared() override;
 
   // media_router::MediaRoutesObserver:
   void OnRoutesUpdated(const std::vector<media_router::MediaRoute>& routes,
@@ -111,9 +113,10 @@ class MediaRouterAction : public ToolbarActionViewController,
   // routes since |this| is an IssueObserver and MediaRoutesObserver.
   gfx::VectorIconId current_icon_;
 
-  // The current issue shown in the Media Router WebUI. Can be null. It is set
-  // in OnIssueUpdated(), which is called by the IssueManager.
-  std::unique_ptr<media_router::Issue> issue_;
+  // The current issue shown in the Media Router WebUI, or not set if there are

[msw, 2016/12/13 18:45:39]

nit: this comment mentions OnIssueUpdated, which no longer exists. Consider:
"The current issue shown in the Media Router WebUI, set in OnIssue() and cleared
in OnIssuesCleared()." or similar.

[imcheng, 2016/12/13 19:22:47]

Done.

+  // no issues currently.
+  // Set in OnIssueUpdated(), which is called by the IssueManager.
+  base::Optional<media_router::IssueInfo> current_issue_;

[msw, 2016/12/13 18:45:39]

q: Just curious, why is base::Optional better than std::unique_ptr here?

[imcheng, 2016/12/13 19:22:47]

It's mostly identical in terms of how they're used here, so I will change it
back to unique_ptr to avoid extra #include.

 
   // Whether a local displayable active route exists.
   bool has_local_display_route_;