Upstream the Media Router's Issue class.

chrome/browser/media/router/issue_manager.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_MANAGER_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_ISSUE_MANAGER_H_
+
+#include <map>
+
+#include "base/containers/hash_tables.h"
+#include "base/observer_list.h"
+#include "base/threading/thread_checker.h"
+#include "chrome/browser/media/router/issue.h"
+#include "chrome/browser/media/router/issues_observer.h"
+
+namespace media_router {
+
+// IssueManager keeps track of current issues related to casting
+// connectivity and quality.
+// TODO(apacible): Determine what other issues will be handled here.
+class IssueManager {
+ public:
+  IssueManager();
+  ~IssueManager();
+
+  // Adds an issue.
+  // |issue|: Issue to be added. Must have unique ID.
+  void AddIssue(const Issue& issue);
+
+  // Removes an issue when user has noted it is resolved.
+  // |issue_id|: IssueId of the issue to be removed.
+  void ClearIssue(const IssueId& issue_id);
+
+  // Gets the number of unresolved issues.
+  size_t GetIssueCount() const;
+
+  // Removes all unresolved issues.
+  void ClearAllIssues();
+
+  // Removes all unresolved global issues.
+  void ClearGlobalIssues();
+
+  // Removes all unresolved issues with RouteId.
+  // |route_id|: MediaRouteId of the issues to be removed.
+  void ClearIssuesWithRouteId(const MediaRouteId& route_id);
+
+  // Registers |observer| in |issues_observers_|. If there is already an
+  // observer registered with this instance, do nothing. Does not take
+  // ownership of |observer|.
+  // |observer|: IssuesObserver to be registered.
+  void RegisterObserver(IssuesObserver* observer);

[DaleCurtis, 2015/04/30 18:18:15]

Is it IssueObserver in that each observer will be called for every issue, or
IssuesObserver where each observer may be called for multiple issues at once?

[apacible, 2015/04/30 19:02:06]

All IssueObservers will be called for each issue that replaces the 'top issue'
(e.g. high priority to show). We show the 'top issue' in the WebUI.

[Kevin M, 2015/05/01 17:59:18]

PTAL at the newest comments, hopefully it is clearer now.

+
+  // Unregisters |observer| from |issues_observers_|.
+  // |observer|: IssuesObserver to be unregistered.
+  void UnregisterObserver(IssuesObserver* observer);
+
+ private:
+  // Checks if the current top issue has changed. Updates |top_issue_|.
+  // If |top_issue_| has changed, issues in |issues_observers_| will be
+  // notified of the new top issue.
+  void MaybeUpdateTopIssue();
+
+  base::hash_map<IssueId, Issue> media_issue_map_;
+
+  // Not owned by IssueManager.
+  ObserverList<IssuesObserver> issues_observers_;
+
+  Issue* top_issue_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(IssueManager);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_ISSUE_MANAGER_H_