bindings: Makes almost all attributes accessor-type properties.

Source/core/html/HTMLDocument.idl

Index: Source/core/html/HTMLDocument.idl
diff --git a/Source/core/html/HTMLDocument.idl b/Source/core/html/HTMLDocument.idl
index 1b73bc81db7ae852ea5116c288e412b0bab7c450..daa8c685cb9e25a059ffeaa53127b91c63f57583 100644
--- a/Source/core/html/HTMLDocument.idl
+++ b/Source/core/html/HTMLDocument.idl
@@ -24,6 +24,14 @@
 // https://html.spec.whatwg.org/#the-window-object
 
 interface HTMLDocument : Document {
+    // Inheritance of [Unforgeable] attributes is not supported.  So we have to
+    // define the same unforgeable attributes in derived interfaces as well.
+    // See that Document already defined 'location' attribute and this interface
+    // redefine it.
+    // Keep all the definitions consistent.
+    // TODO(yukishiino): Support inheritance of attributes defined on instance.
+    [PutForwards=href, Unforgeable] readonly attribute Location? location;
+
     // https://html.spec.whatwg.org/#Document-partial
 
     // FIXME: *Color should have [TreatNullAs=EmptyString].