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

samples/clock/web/numbers.dart

Index: samples/clock/web/numbers.dart
diff --git a/samples/clock/web/numbers.dart b/samples/clock/web/numbers.dart
index 36007a96731e845187553c7c0e5377a47b8dbb0f..5088f83281832da70dbac9ff4edf46ce829f9969 100644
--- a/samples/clock/web/numbers.dart
+++ b/samples/clock/web/numbers.dart
@@ -43,7 +43,7 @@ class ClockNumber {
 
         if (pixels != null) {
           if ((pixels[y][x] != 0) && (px[y][x] == 0)) {
-            window.setImmediate(() {
+            window.immediate.then((_) {
               var r = img.getBoundingClientRect();
               double absx = r.left;
               double absy = r.top;