[MR] Cancel auto-switching from tab mirroring to Cast SDK at page navigation based on user pref

chrome/browser/media/router/media_source_helper.cc

Index: chrome/browser/media/router/media_source_helper.cc
diff --git a/chrome/browser/media/router/media_source_helper.cc b/chrome/browser/media/router/media_source_helper.cc
index 2365cdd9caa0a19eab37a22a437605b513bf66fe..5c585f0eeb662bd986ee84c9a5842edcfa4a0541 100644
--- a/chrome/browser/media/router/media_source_helper.cc
+++ b/chrome/browser/media/router/media_source_helper.cc
@@ -23,6 +23,10 @@ constexpr char kDesktopMediaUrn[] = "urn:x-org.chromium.media:source:desktop";
 constexpr char kTabRemotingUrnFormat[] =
     "urn:x-org.chromium.media:source:tab_content_remoting:%d";
 
+// This value must be the same as |chrome.cast.AUTO_JOIN_PRESENTATION_ID| in the
+// component extension.
+constexpr char kAutoJoinPresentationId[] = "auto-join";
+
 }  // namespace
 
 MediaSource MediaSourceForTab(int tab_id) {
@@ -79,4 +83,8 @@ bool IsValidPresentationUrl(const GURL& url) {
   return url.is_valid() && url.SchemeIsHTTPOrHTTPS();
 }
 
+bool IsAutoJoinPresentationId(const std::string& presentation_id) {
+  return presentation_id == kAutoJoinPresentationId;
+}
+
 }  // namespace media_router