dart:html perf optimization based on runing Dromaeo benchmarks

samples/third_party/dromaeo/tests/dom-query.html

Index: samples/third_party/dromaeo/tests/dom-query.html
diff --git a/samples/third_party/dromaeo/tests/dom-query.html b/samples/third_party/dromaeo/tests/dom-query.html
index bc1d9098a26a295d826e2cbd644f395aa085f298..fc260f3edc190fa6490d2df290310ffd6ce4830f 100644
--- a/samples/third_party/dromaeo/tests/dom-query.html
+++ b/samples/third_party/dromaeo/tests/dom-query.html
@@ -44,35 +44,45 @@ var html = document.body.innerHTML;
 	test( "getElementsByTagName(div)", function(){
 		for ( var i = 0; i < num; i++ ) {
 			var elems = document.getElementsByTagName("div");
-			ret = elems[elems.length-1].nodeType;
+      for (var j = 0, len = elems.length; j < len; j++) {
+        ret = elems[j].hidden;
+      }
 		}
 	});
 
 	test( "getElementsByTagName(p)", function(){
 		for ( var i = 0; i < num; i++ ) {
 			var elems = document.getElementsByTagName("p");
-			ret = elems[elems.length-1].nodeType;
+      for (var j = 0, len = elems.length; j < len; j++) {
+        ret = elems[j].hidden;
+      }
 		}
 	});
 
 	test( "getElementsByTagName(a)", function(){
 		for ( var i = 0; i < num; i++ ) {
 			var elems = document.getElementsByTagName("a");
-			ret = elems[elems.length-1].nodeType;
+      for (var j = 0, len = elems.length; j < len; j++) {
+        ret = elems[j].hidden;
+      }
 		}
 	});
 
 	test( "getElementsByTagName(*)", function(){
 		for ( var i = 0; i < num; i++ ) {
 			var elems = document.getElementsByTagName("*");
-			ret = elems[elems.length-1].nodeType;
+      for (var j = 0, len = elems.length; j < len; j++) {
+        ret = elems[j].hidden;
+      }
 		}
 	});
 
 	test( "getElementsByTagName (not in document)", function(){
 		for ( var i = 0; i < num; i++ ) {
 			var elems = document.getElementsByTagName("strong");
-			ret = elems.length == 0;
+      for (var j = 0, len = elems.length; j < len; j++) {
+        ret = elems[j].hidden;
+      }
 		}
 	});