Begin adding support for tab mirroring via the MediaStream audio/video capturing

content/browser/renderer_host/media/media_stream_provider.h

Index: content/browser/renderer_host/media/media_stream_provider.h
diff --git a/content/browser/renderer_host/media/media_stream_provider.h b/content/browser/renderer_host/media/media_stream_provider.h
index 6218b2e9523f54447a396ba34af2f5d6b6547b42..43292f5b371c682f5e906762f35234867951f60d 100644
--- a/content/browser/renderer_host/media/media_stream_provider.h
+++ b/content/browser/renderer_host/media/media_stream_provider.h
@@ -15,6 +15,7 @@
 #include <list>
 #include <string>
 
+#include "base/memory/ref_counted.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
 
@@ -61,7 +62,8 @@ class CONTENT_EXPORT MediaStreamProviderListener {
 };
 
 // Implemented by a manager class providing captured media.
-class CONTENT_EXPORT MediaStreamProvider {
+class CONTENT_EXPORT MediaStreamProvider
+    : public base::RefCountedThreadSafe<MediaStreamProvider> {
  public:
   // Registers a listener and a device message loop.
   virtual void Register(MediaStreamProviderListener* listener,
@@ -83,6 +85,7 @@ class CONTENT_EXPORT MediaStreamProvider {
   virtual void Close(int capture_session_id) = 0;
 
  protected:
+  friend class base::RefCountedThreadSafe<MediaStreamProvider>;
   virtual ~MediaStreamProvider() {}
 };