Remove files that have already been ported or do not need to be ported.

client/html/src/DOMWrapperBase.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-class DOMWrapperBase {
-  final _ptr;
-
-  DOMWrapperBase._wrap(this._ptr) {
-        // We should never be creating duplicate wrappers.
-        // TODO(jacobr): this boolean value is evaluated outside of the assert
-        // to work around a mysterious and flaky bug in tip of trunk versions of
-        // chrome.
-        bool hasExistingWrapper = _ptr.dartObjectLocalStorage === null;
-        assert(hasExistingWrapper);
-        _ptr.dartObjectLocalStorage = this;
-  }
-}
-
-/** This function is provided for unittest purposes only. */
-unwrapDomObject(DOMWrapperBase wrapper) {
-  return wrapper._ptr;
-}