[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_source.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_MEDIA_SOURCE_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SOURCE_H_
 
+#include <ostream>
 #include <string>
 
 namespace media_router {
 
+using MediaSourceId = std::string;
+
 class MediaSource {
  public:
-  explicit MediaSource(const std::string& id);
+  explicit MediaSource(const MediaSourceId& id);
+  MediaSource();
   ~MediaSource();
 
   // Gets the ID of the media source.
-  std::string id() const;
+  MediaSourceId id() const;
+
+  // Returns true if two MediaSource objects use the same media ID.
+  bool Equals(const MediaSource& other) const;
+
+  // Returns true if a MediaSource is empty or uninitialized.
+  bool Empty() const;
+
+  // Stream output, used for logging.
+  friend std::ostream& operator<<(std::ostream& output,
+                                  const MediaSource& source);

[xhwang, 2015/04/02 17:13:03]

Operator overloading is not recommended:
https://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Operator_Ove...

Can you do something like ToString()?

[imcheng, 2015/04/02 23:05:24]

Done.

 
  private:
-  std::string id_;
+  MediaSourceId id_;

[xhwang, 2015/04/02 17:13:03]

Do we plan to add more members to MeidaSource? Can we just

using MeidaSource = std::string?

Then you don't need Equals/Empty/operator<</etc

[imcheng, 2015/04/02 23:05:24]

It is possible that we will add more fields to MediaSource.

+};
+
+// Inequality comparison functor to provide map lookup capabilities for
+// MediaSource.
+class MediaSourceLess {
+ public:
+  bool operator()(const MediaSource& lhs, const MediaSource& rhs) const {
+    return lhs.id() < rhs.id();
+  }

[xhwang, 2015/04/02 17:13:03]

How will this be used?

[imcheng, 2015/04/02 23:05:24]

It will be used in maps where MediaSource is used as keys. (e.g.
MediaSinksObservers by MediaSource)

[xhwang, 2015/04/06 20:51:30]

Can you simply use MediaSource::id() as the key to this map?

[imcheng, 2015/04/06 21:54:20]

Perhaps we can do that, but we might add more comparable fields to MediaSource
in the future, so prefer to keep this for now.

 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SOURCE_H_