[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 7c618b98484f291892191195998c60b5550a704d..cbe4420cb42603ff31d1a55b6a29f898dac5b5dc 100644
--- a/chrome/browser/media/router/media_source_helper.cc
+++ b/chrome/browser/media/router/media_source_helper.cc
@@ -24,6 +24,11 @@ constexpr char kTabRemotingUrnFormat[] =
     "urn:x-org.chromium.media:source:tab_content_remoting:%d";
 constexpr char kCastPresentationUrlDomain[] = "google.com";
 constexpr char kCastPresentationUrlPath[] = "/cast";
+
+// 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) {
@@ -91,4 +96,8 @@ 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