Remove a few IDL TODOs that have been fixed in the HTML spec

Source/core/frame/History.idl

 /*
  * Copyright (C) 2007, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 12 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 // https://html.spec.whatwg.org/#the-history-interface
 
 enum ScrollRestoration {"auto", "manual"};
 
 [
     GarbageCollected,
 ] interface History {
-    // TODO(philipj): length is long in the spec, use that or change the spec:
-    // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28789
     readonly attribute unsigned long length;
     // TODO(philipj): The SerializedScriptValue type should be any.
     [CachedAttribute=stateChanged] readonly attribute SerializedScriptValue state;
-    // TODO(philipj): delta does not have a default value in the spec:
-    // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28790
     [CallWith=ExecutionContext] void go(optional long delta = 0);
     [CallWith=ExecutionContext] void back();
     [CallWith=ExecutionContext] void forward();
     // TODO(philipj): The SerializedScriptValue types should be any.
     // TODO(philipj): The title arguments should simply be 'DOMString title'.
     [RaisesException] void pushState(SerializedScriptValue data, [TreatUndefinedAs=NullString] DOMString? title, optional DOMString? url = null);
     [RaisesException] void replaceState(SerializedScriptValue data, [TreatUndefinedAs=NullString] DOMString? title, optional DOMString? url = null);
 
     // Experimental Scroll Restoration API
     // https://www.chromestatus.com/features/5657284784947200
     [RuntimeEnabled=ScrollRestoration] attribute ScrollRestoration scrollRestoration;
 };