Media Session: use dictionary instead of an interface for MediaImage.

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

Index: third_party/WebKit/Source/modules/mediasession/MediaImage.idl
diff --git a/third_party/WebKit/Source/modules/mediasession/MediaImage.idl b/third_party/WebKit/Source/modules/mediasession/MediaImage.idl
index fd33ba78bdc9692238d79bea4f41e1602b601f35..ef4703a1da63cfa0b58910965f03e5d64f58c73d 100644
--- a/third_party/WebKit/Source/modules/mediasession/MediaImage.idl
+++ b/third_party/WebKit/Source/modules/mediasession/MediaImage.idl
@@ -2,14 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// https://wicg.github.io/mediasession/#the-mediaimage-interface
+// https://wicg.github.io/mediasession/#dictdef-mediaimage
 
-[
-    ConstructorCallWith=ExecutionContext,
-    Constructor(MediaImageInit image),
-    RuntimeEnabled=MediaSession,
-] interface MediaImage {
-  readonly attribute USVString src;
-  readonly attribute DOMString sizes;
-  readonly attribute DOMString type;
+dictionary MediaImage {
+  required USVString src;
+  DOMString sizes = "";
+  DOMString type = "";
 };