Pass origin to StartObservingMediaSinks.

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:";
+const char kOrigin[] = "";
 
 MediaSource MediaSourceForTab(int tab_id) {
   return MediaSource(base::StringPrintf("%s:%d", kTabMediaUrnPrefix, tab_id));
 }
 
 MediaSource MediaSourceForDesktop() {
   return MediaSource(std::string(kDesktopMediaUrn));
 }
 
+GURL OriginForDesktop() {

[mark a. foltz, 2016/02/17 21:50:51]

If we need an origin for tab and desktop casting, it would probably be the media
router WebUI, chrome://media-router

https://code.google.com/p/chromium/codesearch#chromium/src/chrome/common/url_...

This is what we pass to CreateRoute()

[matt.boetger, 2016/02/18 00:50:33]

Done.

+  return GURL(std::string(kOrigin));
+}
+
 MediaSource MediaSourceForCastApp(const std::string& app_id) {
   return MediaSource(kCastUrnPrefix + app_id);
 }
 
 MediaSource MediaSourceForPresentationUrl(const std::string& presentation_url) {
   return MediaSource(presentation_url);
 }
 
 bool IsDesktopMirroringMediaSource(const MediaSource& source) {
   return base::StartsWith(source.id(), kDesktopMediaUrn,
@@ skipping 23 matching lines @@
 std::string PresentationUrlFromMediaSource(const MediaSource& source) {
   return IsValidPresentationUrl(source.id()) ? source.id() : "";
 }
 
 bool IsValidPresentationUrl(const std::string& url) {
   GURL gurl(url);
   return gurl.is_valid() && gurl.SchemeIsHTTPOrHTTPS();
 }
 
 }  // namespace media_router