v8binding: Implements an alternative of WindowProxy.[[DefineOwnProperty]].

third_party/WebKit/Source/core/frame/Window.idl

Index: third_party/WebKit/Source/core/frame/Window.idl
diff --git a/third_party/WebKit/Source/core/frame/Window.idl b/third_party/WebKit/Source/core/frame/Window.idl
index c86c8b21790ac6626c5f682a9df2207544a54917..2bbfaa865627a17625dfbc751ada0eb494480289 100644
--- a/third_party/WebKit/Source/core/frame/Window.idl
+++ b/third_party/WebKit/Source/core/frame/Window.idl
@@ -64,8 +64,14 @@
     [CheckSecurity=ReturnValue, Custom=Getter] readonly attribute Element? frameElement;
     // FIXME: open() should have 4 optional arguments with defaults.
     [Custom] Window? open(DOMString url, DOMString target, optional DOMString features);
-    // FIXME: These getters should not have [NotEnumerable].
+
+    // indexed properties
+    // https://html.spec.whatwg.org/C/browsers.html#windowproxy-getownproperty
     [NotEnumerable, CrossOrigin] getter Window (unsigned long index);
+    // https://html.spec.whatwg.org/C/browsers.html#windowproxy-defineownproperty
+    setter void (unsigned long index, any value);
+
+    // named properties
     [Custom, NotEnumerable, CrossOrigin] getter object (DOMString name);
 
     // the user agent