Move dromaeo to third_party

client/dom/benchmarks/dromaeo/tests/dom-attr.dart

-#library("dom-attr.dart");
-#import("dart:dom");
-#import('runner.dart');
-
-void main() {
-  final int num = 10240;
-
-  // Try to force real results.
-  var ret;
-
-  HTMLElement elem = document.getElementById('test1');
-  HTMLElement a = document.getElementsByTagName('a')[0];
-
-  new Suite(window, 'dom-attr')
-    .test('getAttribute', void _() {
-      for (int i = 0; i < num; i++)
-        ret = elem.getAttribute('id');
-    })
-    .test('element.property', () {
-      for (int i = 0; i < num * 2; i++)
-        ret = elem.id;
-    })
-    .test('setAttribute', () {
-        for (int i = 0; i < num; i++)
-        a.setAttribute('id', 'foo');
-    })
-    .test('element.property = value', () {
-      for (int i = 0; i < num; i++)
-        a.id = 'foo';
-    })
-    .end();
-}