Fix identity and SVGAnimatedString issues with element_classes_test

tools/dom/templates/html/impl/impl_Element.darttemplate

 // Copyright (c) 2012, 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.
 
 part of $LIBRARYNAME;
 
 class _ChildrenElementList extends ListBase<Element>
     implements NodeListWrapper {
   // Raw Element.
   final Element _element;
@@ skipping 79 matching lines @@
     throw new UnimplementedError();
   }
 
   void fillRange(int start, int end, [Element fillValue]) {
     throw new UnimplementedError();
   }
 
   bool remove(Object object) {
     if (object is Element) {
       Element element = object;
+$if JSINTEROP
+      // We aren't preserving identity of nodes in JSINTEROP mode
+      if (element.parentNode == _element) {
+$else
       if (identical(element.parentNode, _element)) {
+$endif
         _element._removeChild(element);
         return true;
       }
     }
     return false;
   }
 
   void insert(int index, Element element) {
     if (index < 0 || index > length) {
       throw new RangeError.range(index, 0, length);
@@ skipping 1141 matching lines @@
   @Experimental()
   Point offsetTo(Element parent) {
     return Element._offsetToHelper(this, parent);
   }
 
   static Point _offsetToHelper(Element current, Element parent) {
     // We're hopping from _offsetParent_ to offsetParent (not just parent), so
     // offsetParent, "tops out" at BODY. But people could conceivably pass in
     // the document.documentElement and I want it to return an absolute offset,
     // so we have the special case checking for HTML.
-    bool foundAsParent = identical(current, parent) || parent.tagName == 'HTML';
-    if (current == null || identical(current, parent)) {
+$if JSINTEROP

[terry, 2015/08/17 14:40:29]

Comment?

// We aren't preserving identity of nodes in JSINTEROP mode

+    bool sameAsParent = current == parent;
+$else
+    bool sameAsParent = identical(current, parent);
+$endif
+    bool foundAsParent = sameAsParent || parent.tagName == 'HTML';
+    if (current == null || sameAsParent) {
       if (foundAsParent) return new Point(0, 0);
       throw new ArgumentError("Specified element is not a transitive offset "
           "parent of this element.");
     }
     Element parentOffset = current.offsetParent;
     Point p = Element._offsetToHelper(parentOffset, parent);
     return new Point(p.x + current.offsetLeft, p.y + current.offsetTop);
   }
 
   static HtmlDocument _parseDocument;
@@ skipping 396 matching lines @@
   const ScrollAlignment._internal(this._value);
   toString() => 'ScrollAlignment.$_value';
 
   /// Attempt to align the element to the top of the scrollable area.
   static const TOP = const ScrollAlignment._internal('TOP');
   /// Attempt to center the element in the scrollable area.
   static const CENTER = const ScrollAlignment._internal('CENTER');
   /// Attempt to align the element to the bottom of the scrollable area.
   static const BOTTOM = const ScrollAlignment._internal('BOTTOM');
 }