Remove the concept of document.documentElement

sky/tests/services/event-sender.sky

Index: sky/tests/services/event-sender.sky
diff --git a/sky/tests/services/event-sender.sky b/sky/tests/services/event-sender.sky
index 2c346b4f012c961723f7ce0af24973375e394e08..b72ab9c1aad231d1f5110e4c353755b2a59d0592 100644
--- a/sky/tests/services/event-sender.sky
+++ b/sky/tests/services/event-sender.sky
@@ -13,8 +13,7 @@ void main() {
   initUnit();
 
   test('should be able to send events', () {
-    var sky = document.querySelector('sky');
-    sky.addEventListener('keypress', expectAsync((event) {
+    document.addEventListener('keypress', expectAsync((event) {
       expect(event.type, equals('keypress'));
       expect(event.key, equals(0));
       expect(event.charCode, equals(0x41));