Make ~/, round, ceil, floor, truncate return ints. Remove toInt.

samples/swarm/swarm_ui_lib/touch/Momentum.dart

Index: samples/swarm/swarm_ui_lib/touch/Momentum.dart
diff --git a/samples/swarm/swarm_ui_lib/touch/Momentum.dart b/samples/swarm/swarm_ui_lib/touch/Momentum.dart
index 4ed97e717a9c72aeec0dcdc30b2dc09b01fc7713..3940d0b11999dd91cf24381771c5976f4bbd9760 100644
--- a/samples/swarm/swarm_ui_lib/touch/Momentum.dart
+++ b/samples/swarm/swarm_ui_lib/touch/Momentum.dart
@@ -479,9 +479,8 @@ class TimeoutMomentum implements Momentum {
   void _stepWithoutAnimation() {
     physicsX.step();
     physicsY.step();
-    // TODO(jacobr): double.round() should return an int, see b/5121907
-    _nextX = physicsX._currentOffset.round().toInt();
-    _nextY = physicsY._currentOffset.round().toInt();
+    _nextX = physicsX._currentOffset.round();
+    _nextY = physicsY._currentOffset.round();
   }
 
   /**