[MediaRouter] Add implementation of PresentationServiceDelegate

chrome/browser/media/router/media_source_helper.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_HELPER_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SOURCE_HELPER_H_
 
 #include <string>
 
 #include "chrome/browser/media/router/media_source.h"
 
 namespace media_router {
 
 // Helper library for protocol-specific media source object creation.
-
-// TODO(kmarshall): Should these creation methods be moved to the WebUI, which
-// (excluding Presentation API) is their only caller? The MR base code can be
-// Also, consider generating an is_mirroring state boolean at the time of URN
-// creation so that the mirroring status does not have to be determined from a
-// string prefix check.
-// These changes would allow the MR to handle MediaSource objects in the same
-// type agnostic fashion vs. having to format and parse URNs and track which
-// MediaSource types are mirroring-enabled.
-
 // Returns MediaSource URI depending on the type of source.
-MediaSource ForTabMediaSource(int tab_id);
-MediaSource ForDesktopMediaSource();
-MediaSource ForCastAppMediaSource(const std::string& app_id);
-MediaSource ForPresentationUrl(const std::string& presentation_url);
+MediaSource MediaSourceForTab(int tab_id);
+MediaSource MediaSourceForDesktop();
+MediaSource MediaSourceForCastApp(const std::string& app_id);
+MediaSource MediaSourceForPresentationUrl(const std::string& presentation_url);
 
 // Returns true if |source| outputs its content via mirroring.
 bool IsMirroringMediaSource(const MediaSource& source);
 
 // Checks that |source| is a parseable URN and is of a known type.
 // Does not deeper protocol-level syntax checks.
 bool IsValidMediaSource(const MediaSource& source);
 
+// Extracts the presentation URL from |source|.
+// If |source| is invalid, an empty string is returned.
+std::string PresentationUrlFromMediaSource(const MediaSource& source);
+
+// Returns true if |source| is a valid presentation URL.
+bool IsValidPresentationUrl(const std::string& url);
+
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SOURCE_HELPER_H_