Add media controls to MediaSession in Blink

third_party/WebKit/Source/modules/mediasession/MediaSession.idl

Index: third_party/WebKit/Source/modules/mediasession/MediaSession.idl
diff --git a/third_party/WebKit/Source/modules/mediasession/MediaSession.idl b/third_party/WebKit/Source/modules/mediasession/MediaSession.idl
index 617484209899e6eccf81c439bbd466c11f33eef6..aacbeb4223e8f06a81ac835e35147b81c666e9f2 100644
--- a/third_party/WebKit/Source/modules/mediasession/MediaSession.idl
+++ b/third_party/WebKit/Source/modules/mediasession/MediaSession.idl
@@ -6,6 +6,14 @@
 
 [
     RuntimeEnabled=MediaSession,
-] interface MediaSession {
-    [CallWith=ScriptState] attribute MediaMetadata? metadata;
+] interface MediaSession : EventTarget {
+    attribute MediaMetadata? metadata;
+
+    attribute EventHandler onplay;
+    attribute EventHandler onpause;
+    attribute EventHandler onplaypause;
+    attribute EventHandler onprevioustrack;
+    attribute EventHandler onnexttrack;
+    attribute EventHandler onseekforward;
+    attribute EventHandler onseekbackward;
 };