Combine window.setTimeout/setInterval with Timer and Timer.repeating. Also

samples/calculator/tape.dart

Index: samples/calculator/tape.dart
diff --git a/samples/calculator/tape.dart b/samples/calculator/tape.dart
index fb9d5e53c183dddb58072df26deb2b2838c789d5..55f94f318b6a19be72caeb5de93956884676c723 100644
--- a/samples/calculator/tape.dart
+++ b/samples/calculator/tape.dart
@@ -189,7 +189,7 @@ class Tape {
   }
 
   void scrollToTapeBottom() {
-    window.setImmediate(() {
+    window.immediate.then((_) {
       // theTape.rect.scroll.top = rect.scroll.height;
       // TODO(terry): Would like to set scrollTop of tape doesn't seem to work
       //              so I scroll by max lines.