Further code review changes for issue 8341027.

client/html/src/DocumentFragmentWrappingImplementation.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 FilteredElementList implements ElementList {
   final Node _node;
   final NodeList _childNodes;
 
   FilteredElementList(Node node): _childNodes = node.nodes, _node = node;
 
@@ skipping 90 matching lines @@
     _filtered.getRange(start, length);
   int indexOf(Element element, int startIndex) =>
     _filtered.indexOf(element, startIndex);
   int lastIndexOf(Element element, int startIndex) =>
     _filtered.lastIndexOf(element, startIndex);
   Element last() => _filtered.last();
 }
 
 class EmptyStyleDeclaration extends CSSStyleDeclarationWrappingImplementation {
   // This can't call super(), since that's a factory constructor
-  EmptyStyleDeclaration()
-    : super._wrap(dom.document.createElement('div').style);
+  const EmptyStyleDeclaration() : super._empty();
+
+  String get cssText() => "";
+  int get length() => 0;
+  CSSRule get parentRule() => null;
+  CSSValue getPropertyCSSValue(String propertyName) => null;    
+  String getPropertyPriority(String propertyName) => "";        
+  String getPropertyShorthand(String propertyName) => null;     
+  String getPropertyValue(String propertyName) => null; 
+  bool isPropertyImplicit(String propertyName) => false;        
+  String item(int index) => "";
 
   void set cssText(String value) {
     throw new UnsupportedOperationException(
         "Can't modify a frozen style declaration.");
   }
 
   String removeProperty(String propertyName) {
     throw new UnsupportedOperationException(
         "Can't modify a frozen style declaration.");
   }
 
   void setProperty(String propertyName, String value, [String priority]) {
     throw new UnsupportedOperationException(
         "Can't modify a frozen style declaration.");
   }
 }
 
 class EmptyClientRect implements ClientRect {
   num get bottom() => 0;
   num get top() => 0;
   num get left() => 0;
   num get right() => 0;
   num get height() => 0;
   num get width() => 0;
 }
 
 class DocumentFragmentWrappingImplementation extends NodeWrappingImplementation implements DocumentFragment {
   ElementList _elements;
+  CSSStyleDeclaration _style;
+  ClientRect _clientRect;
 
   DocumentFragmentWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
 
   factory DocumentFragmentWrappingImplementation() {
     return new DocumentFragmentWrappingImplementation._wrap(
             dom.document.createDocumentFragment());
   }
 
   factory DocumentFragmentWrappingImplementation.html(String html) {
     var fragment = new DocumentFragment();
@@ skipping 70 matching lines @@
     }
     return _on;
   }
 
   Element query(String selectors) =>
     LevelDom.wrapElement(_ptr.querySelector(selectors));
 
   ElementList queryAll(String selectors) =>
     LevelDom.wrapElementList(_ptr.querySelectorAll(selectors));
 
+  CSSStyleDeclaration get style() {
+    if (_style == null) _style = const EmptyStyleDeclaration();
+    return _style;
+  }
+
+  ClientRect getBoundingClientRect() {
+    if (_clientRect == null) _clientRect = new EmptyClientRect();
+    return _clientRect;
+  }
+
   // If we can come up with a semi-reasonable default value for an Element
   // getter, we'll use it. In general, these return the same values as an
   // element that has no parent.
   int get clientHeight() => 0;
   int get clientWidth() => 0;
   int get offsetHeight() => 0;
   int get offsetWidth() => 0;
   int get scrollHeight() => 0;
   int get scrollWidth() => 0;
   int get clientLeft() => 0;
@@ skipping 15 matching lines @@
   Element get firstElementChild() => elements.first();
   Element get lastElementChild() => elements.last();
   Element get nextElementSibling() => null;
   Element get previousElementSibling() => null;
   Element get offsetParent() => null;
   Element get parent() => null;
   Map<String, String> get attributes() => const {};
   // Issue 174: this should be a const set.
   Set<String> get classes() => new Set<String>();
   Map<String, String> get dataAttributes() => const {};
-  CSSStyleDeclaration get style() => new EmptyStyleDeclaration();
-  ClientRect getBoundingClientRect() => new EmptyClientRect();
   List<ClientRect> getClientRects() => const [];
   bool matchesSelector([String selectors]) => false;
 
   // Imperative Element methods are made into no-ops, as they are on parentless
   // elements.
   void blur() {}
   void focus() {}
   void scrollByLines([int lines]) {}
   void scrollByPages([int pages]) {}
   void scrollIntoView([bool centerIfNeeded]) {}
@@ skipping 78 matching lines @@
   void set title(String value) {
     throw new UnsupportedOperationException(
       "Title can't be set for document fragments.");
   }
 
   void set webkitdropzone(String value) {
     throw new UnsupportedOperationException(
       "WebKit drop zone can't be set for document fragments.");
   }
 }