Roll 50: Copied IDLs, PYTHON scripts from WebKit removed deleted files in WebCore

modules/mediasession/MediaSession.idl

Index: modules/mediasession/MediaSession.idl
diff --git a/modules/mediasession/MediaSession.idl b/modules/mediasession/MediaSession.idl
index 235604b3f20f4b98c5470611e3d8e68f8152db2e..b09cbc31d3fc566c19522ca8604345d0d17b4f39 100644
--- a/modules/mediasession/MediaSession.idl
+++ b/modules/mediasession/MediaSession.idl
@@ -6,9 +6,13 @@
 
 [
     Constructor(),
+    ConstructorCallWith=ExecutionContext,
+    RaisesException=Constructor,
     GarbageCollected,
     RuntimeEnabled=MediaSession,
 ] interface MediaSession {
-    void activate();
-    void deactivate();
+    attribute MediaMetadata? metadata;
+
+    [CallWith=ScriptState] Promise<void> activate();
+    [CallWith=ScriptState] Promise<void> deactivate();
 };