Add browser test cases for tab and audio share, which are new functionality of desktop share.

content/public/browser/desktop_media_id.h

Index: content/public/browser/desktop_media_id.h
diff --git a/content/public/browser/desktop_media_id.h b/content/public/browser/desktop_media_id.h
index 5db272a339e093783edd5dbafd45ec513dcf3924..7b6cd1f101101d321078ada647d92e7ed0becd32 100644
--- a/content/public/browser/desktop_media_id.h
+++ b/content/public/browser/desktop_media_id.h
@@ -46,6 +46,9 @@ struct CONTENT_EXPORT DesktopMediaID {
   DesktopMediaID(Type type, Id id, WebContentsMediaCaptureId web_contents_id)
       : type(type), id(id), web_contents_id(web_contents_id) {}
 
+  DesktopMediaID(Type type, Id id, bool audio_share)
+      : type(type), id(id), audio_share(audio_share) {}
+
   // Operators so that DesktopMediaID can be used with STL containers.
   bool operator<(const DesktopMediaID& other) const;
   bool operator==(const DesktopMediaID& other) const;