Make querySelectorAll a generic method so that checked mode behavior is consistent with existing be…

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 a2ea4fa5a45d8f68655e5b9cdac8f28e036ea924..d45b265d895c1a6851480bfb552727fbd1d9585c 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -264,8 +264,8 @@ $!STREAM_GETTER_SIGNATURES
 // declared to return `ElementList`.  This provides all the static analysis
 // benefit so there is no need for this class have a constrained type parameter.
 //
-class _FrozenElementList extends ListBase<Element>
-    implements ElementList<Element>, NodeListWrapper {
+class _FrozenElementList<E extends Element> extends ListBase<E>
+    implements ElementList<E>, NodeListWrapper {
   final List<Node> _nodeList;
 
 $if JSINTEROP
@@ -280,9 +280,9 @@ $endif
 
   int get length => _nodeList.length;
 
-  Element operator [](int index) => _nodeList[index];
+  E operator [](int index) => _nodeList[index] as E;
 
-  void operator []=(int index, Element value) {
+  void operator []=(int index, E value) {
     throw new UnsupportedError('Cannot modify list');
   }
 
@@ -290,7 +290,7 @@ $endif
     throw new UnsupportedError('Cannot modify list');
   }
 
-  void sort([Comparator<Element> compare]) {
+  void sort([Comparator<E> compare]) {
     throw new UnsupportedError('Cannot sort list');
   }
 
@@ -298,11 +298,11 @@ $endif
     throw new UnsupportedError('Cannot shuffle list');
   }
 
-  Element get first => _nodeList.first;
+  E get first => _nodeList.first as E;
 
-  Element get last => _nodeList.last;
+  E get last => _nodeList.last as E;
 
-  Element get single => _nodeList.single;
+  E get single => _nodeList.single as E;
 
   CssClassSet get classes => new _MultiElementCssClassSet(this);
 
@@ -611,8 +611,8 @@ $endif
    * [CSS selector specification](http://www.w3.org/TR/css3-selectors/).
    */
   @DomName('Element.querySelectorAll')
-  ElementList<Element> querySelectorAll(String selectors) =>
-    new _FrozenElementList._wrap(_querySelectorAll(selectors));
+  ElementList/*<T>*/ querySelectorAll/*<T extends Element>*/(String selectors) =>
+    new _FrozenElementList/*<T>*/._wrap(_querySelectorAll(selectors));
 
   /**
    * Alias for [querySelector]. Note this function is deprecated because its