Make MediaSession per frame as an attribute of Navigator

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

Index: third_party/WebKit/Source/modules/mediasession/NavigatorMediaSession.idl
diff --git a/third_party/WebKit/Source/modules/webshare/NavigatorShare.idl b/third_party/WebKit/Source/modules/mediasession/NavigatorMediaSession.idl
similarity index 52%
copy from third_party/WebKit/Source/modules/webshare/NavigatorShare.idl
copy to third_party/WebKit/Source/modules/mediasession/NavigatorMediaSession.idl
index 27e55b463664f32e5317e445c4edeba3d1084bbe..39ef8d04a981063ee45f04c514b5a77f65f24d03 100644
--- a/third_party/WebKit/Source/modules/webshare/NavigatorShare.idl
+++ b/third_party/WebKit/Source/modules/mediasession/NavigatorMediaSession.idl
@@ -2,11 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// https://github.com/WICG/web-share/blob/master/docs/interface.md
+// https://wicg.github.io/mediasession/#the-mediasession-interface
 
 [
-  OriginTrialEnabled=WebShare,
+    Exposed=(Window),
+    RuntimeEnabled=MediaSession
 ] partial interface Navigator {
-  [CallWith=ScriptState, MeasureAs=WebShareShare]
-  Promise<void> share(ShareData data);
+    readonly attribute MediaSession mediaSession;
 };