dart:html perf optimization based on runing Dromaeo benchmarks

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

Index: samples/third_party/dromaeo/tests/dom-query-html.dart
diff --git a/samples/third_party/dromaeo/tests/dom-query-html.dart b/samples/third_party/dromaeo/tests/dom-query-html.dart
index 8e590ecd7e663fb26f8e48a1c434a4be7f55215e..9e7f62a6fcc93e2c09343e92bf3097ad5b0ccca6 100644
--- a/samples/third_party/dromaeo/tests/dom-query-html.dart
+++ b/samples/third_party/dromaeo/tests/dom-query-html.dart
@@ -50,37 +50,47 @@ void main() {
     })
     .test('getElementsByTagName(div)', () {
       for (int i = 0; i < num; i++) {
-        var elems = document.queryAll('div');
-        ret = elems.last().hidden;
+        ElementList elems = document.queryAll('div');
+        for (int j = 0, len = elems.length; j < len; j++) {
+          ret = elems[j].hidden;
+        }
       }
     })
     .test('getElementsByTagName(p)', () {
       for (int i = 0; i < num; i++) {
-        final elems = document.queryAll('p');
-        ret = elems.last().hidden;
+        ElementList elems = document.queryAll('p');
+        for (int j = 0, len = elems.length; j < len; j++) {
+          ret = elems[j].hidden;
+        }
       }
     })
     .test('getElementsByTagName(a)', () {
       for (int i = 0; i < num; i++) {
-        var elems = document.queryAll('a');
-        ret = elems.last().hidden;
+        ElementList elems = document.queryAll('a');
+        for (int j = 0, len = elems.length; j < len; j++) {
+          ret = elems[j].hidden;
+        }
       }
     })
     .test('getElementsByTagName(*)', () {
       for (int i = 0; i < num; i++) {
-        var elems = document.queryAll('*');
-        ret = elems.last().hidden;
+        ElementList elems = document.queryAll('*');
+        for (int j = 0, len = elems.length; j < len; j++) {
+          ret = elems[j].hidden;
+        }
       }
     })
     .test('getElementsByTagName (not in document)', () {
       for (int i = 0; i < num; i++) {
-        var elems = document.queryAll('strong');
-        ret = elems.length == 0;
+        ElementList elems = document.queryAll('strong');
+        for (int j = 0, len = elems.length; j < len; j++) {
+          ret = elems[j].hidden;
+        }
       }
     })
     .test('getElementsByName', () {
       for (int i = 0; i < num * 20; i++) {
-        var elems = document.queryAll('[name="test$num"]');
+        ElementList elems = document.queryAll('[name="test$num"]');
         ret = elems.last().hidden;
         elems = document.queryAll('[name="test$num"]');
         ret = elems.last().hidden;