Implement MediaMetadata artwork in content

content/browser/media/android/browser_media_session_manager.h

Index: content/browser/media/android/browser_media_session_manager.h
diff --git a/content/browser/media/android/browser_media_session_manager.h b/content/browser/media/android/browser_media_session_manager.h
index b936ba03e557ef456edf487725de46a4982603cb..cd92bdc746c8ee029ca3ef3b09c6c4b1cc8da3bb 100644
--- a/content/browser/media/android/browser_media_session_manager.h
+++ b/content/browser/media/android/browser_media_session_manager.h
@@ -6,6 +6,7 @@
 #define CONTENT_BROWSER_MEDIA_ANDROID_BROWSER_MEDIA_SESSION_MANAGER_H_
 
 #include "base/macros.h"
+#include "content/common/content_export.h"
 
 namespace IPC {
 class Message;
@@ -16,14 +17,14 @@ namespace content {
 class RenderFrameHost;
 struct MediaMetadata;
 
-class BrowserMediaSessionManager {
+class CONTENT_EXPORT BrowserMediaSessionManager {
  public:
-  BrowserMediaSessionManager(RenderFrameHost* render_frame_host);
+  explicit BrowserMediaSessionManager(RenderFrameHost* render_frame_host);
 
   // Message handlers.
-  void OnActivate(int session_id, int request_id);
-  void OnDeactivate(int session_id, int request_id);
-  void OnSetMetadata(int session_id, const MediaMetadata& metadata);
+  virtual void OnActivate(int session_id, int request_id);
+  virtual void OnDeactivate(int session_id, int request_id);
+  virtual void OnSetMetadata(int session_id, const MediaMetadata& metadata);
 
   int GetRoutingID() const;