Reland "Adding media controls to MediaNotification"

content/public/browser/media_session.h

Index: content/public/browser/media_session.h
diff --git a/content/public/browser/media_session.h b/content/public/browser/media_session.h
index 9d92b77eaf598ff570fc21347bb87482236ccb48..78a18898d4c8b414e6416a277d490781c9bf5057 100644
--- a/content/public/browser/media_session.h
+++ b/content/public/browser/media_session.h
@@ -8,6 +8,12 @@
 #include "base/macros.h"
 #include "content/common/content_export.h"
 
+namespace blink {
+namespace mojom {
+enum class MediaSessionAction;
+}  // namespace mojom
+}  // namespace blink
+
 namespace content {
 
 class WebContents;
@@ -46,6 +52,9 @@ class MediaSession {
   // |type| represents the origin of the request.
   virtual void Stop(SuspendType suspend_type) = 0;
 
+  // Tell the media session a user action has performed.
+  virtual void DidReceiveAction(blink::mojom::MediaSessionAction action) = 0;
+
  protected:
   MediaSession() = default;
 };