Gets presentation ID from route ID upon route creation, and overrides previous presentation ID with…

chrome/browser/media/router/media_route.h

Index: chrome/browser/media/router/media_route.h
diff --git a/chrome/browser/media/router/media_route.h b/chrome/browser/media/router/media_route.h
index e8d270ae7dba683e6ff9880ac0f363c1320ed57f..8e47ee36db31ec77fe5ff50a4789802c9b776298 100644
--- a/chrome/browser/media/router/media_route.h
+++ b/chrome/browser/media/router/media_route.h
@@ -79,6 +79,11 @@ class MediaRoute {
   MediaRouteState state_;
 };
 
+// Return a pair of Presentation ID and URL. If the input route ID is invalid,
+// a pair of empty strings is returned.

[Kevin M, 2015/06/24 23:02:07]

If a caller is going to use half the pair but discard the other half, then this
should be split into 2 functions vs. returning a pair to save on unnecessary
processing.

I recommend just making an additional function that takes a computed
presentation URL and returns a StringPiece representing the source substr.

[Kevin M, 2015/06/24 23:02:07]

Presentation API support functions should be in preso API files.

[Kevin M, 2015/06/24 23:02:07]

Document the parameters and return type

[haibinlu, 2015/06/24 23:25:12]

Ack. Constructing presentation session message is done here. Moving it to
presention_service_delegate_impl makes sense, but incurs extra cost of blinding
message_callback to itself, pass media_router.mojo's route message format, etc.

To avoid using media_router.mojo's route message format in presentation files,
we need to create another class shared by both, an unnecessary cost for carrying
message along.

[haibinlu, 2015/06/24 23:25:13]

They are obvious in method signature. Not sure about the value of adding more
doc.

[haibinlu, 2015/06/24 23:25:13]

yes, there are lot more fields in the route-id. I do not want to do it in the
CL. Prefer a separate CL for refactoring source/sink/route URN.

+std::pair<std::string, std::string> GetPresentationIdAndUrl(
+    const MediaRoute::Id& id);
+
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTE_H_