[MediaRouter] Add implementation of PresentationServiceDelegate

chrome/browser/media/router/media_source_helper.cc

 // 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.
 
 #include "chrome/browser/media/router/media_source_helper.h"
 
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/media/router/media_source.h"
 #include "url/gurl.h"
 
 namespace media_router {
 
 // Prefixes used to format and detect various protocols' media source URNs.
 // See: https://www.ietf.org/rfc/rfc3406.txt
 const char kTabMediaUrnPrefix[] = "urn:x-org.chromium.media:source:tab";
 const char kDesktopMediaUrn[] = "urn:x-org.chromium.media:source:desktop";
 const char kCastUrnPrefix[] = "urn:x-com.google.cast:application:";
 
 MediaSource ForTabMediaSource(int tab_id) {
   return MediaSource(base::StringPrintf("%s:%d", kTabMediaUrnPrefix, tab_id));
 }
 
 MediaSource ForDesktopMediaSource() {
   return MediaSource(std::string(kDesktopMediaUrn));
 }
 
 // TODO(mfoltz): Remove when the TODO in
-// MediaSourceManager::GetDefaultMediaSource is resolved.
+// PresentationServiceDelegateImpl::default_source is resolved.
 MediaSource ForCastAppMediaSource(const std::string& app_id) {
   return MediaSource(kCastUrnPrefix + app_id);
 }
 
 MediaSource ForPresentationUrl(const std::string& presentation_url) {
   return MediaSource(presentation_url);
 }
 
 bool IsMirroringMediaSource(const MediaSource& source) {
   return StartsWithASCII(source.id(), kDesktopMediaUrn, true) ||
     StartsWithASCII(source.id(), kTabMediaUrnPrefix, true);
 }
 
 bool IsValidMediaSource(const MediaSource& source) {
   if (IsMirroringMediaSource(source) ||
       StartsWithASCII(source.id(), kCastUrnPrefix, true)) {
     return true;
   }
   GURL url(source.id());
   return url.is_valid() && url.SchemeIsHTTPOrHTTPS();
 }
 
+std::string GetPresentationUrl(const MediaSource& source) {
+  return IsValidPresentationUrl(source.id()) ? source.id() : "";
+}
+
 }  // namespace media_router