Allow "bulk editing" of the CssStyleDeclaration objects in an ElementList as well

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

Index: tools/dom/templates/html/impl/impl_Element.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Element.darttemplate b/tools/dom/templates/html/impl/impl_Element.darttemplate
index 29533d85e51edf400246ddabfac96794c71a764f..6e932875f22e26c2b130f8e68b94dfac28b76937 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -176,6 +176,9 @@ abstract class ElementList<T extends Element> extends ListBase<T> {
   /** Replace the classes with `value` for every element in this list. */
   set classes(Iterable<String> value);
 
+  /** The union of all styles associated with the [Element]s in this list. */
+  CssStyleDeclarationSet get style;
+
   /** 
    * Access dimensions and position of the Elements in this list.
    * 
@@ -271,6 +274,9 @@ class _FrozenElementList<T extends Element> extends ListBase<T> implements Eleme
 
   CssClassSet get classes => new _MultiElementCssClassSet(_elementList);
 
+  CssStyleDeclarationSet get style => 
+      new CssStyleDeclarationSet._(_elementList);
+
   void set classes(Iterable<String> value) {
     _elementList.forEach((e) => e.classes = value);
   }