Typing fixes to eliminate casts/dcalls

test/dart_codegen/expect/async/timer.dart

 part of dart.async;
  abstract class Timer {factory Timer(Duration duration, void callback()) {
   if (Zone.current == Zone.ROOT) {
     return Zone.current.createTimer(duration, callback);
     }
    return Zone.current.createTimer(duration, Zone.current.bindCallback(callback, runGuarded: true));
   }
  factory Timer.periodic(Duration duration, void callback(Timer timer)) {
   if (Zone.current == Zone.ROOT) {
     return Zone.current.createPeriodicTimer(duration, callback);
     }
-   return Zone.current.createPeriodicTimer(duration, ((__x83) => DEVC$RT.cast(__x83, ZoneUnaryCallback, __CastType81, "CompositeCast", """line 80, column 19 of dart:async/timer.dart: """, __x83 is __CastType81, false))(Zone.current.bindUnaryCallback(callback, runGuarded: true)));
+   return Zone.current.createPeriodicTimer(duration, ((__x78) => DEVC$RT.cast(__x78, ZoneUnaryCallback, __CastType76, "CompositeCast", """line 80, column 19 of dart:async/timer.dart: """, __x78 is __CastType76, false))(Zone.current.bindUnaryCallback(callback, runGuarded: true)));
   }
  static void run(void callback()) {
   new Timer(Duration.ZERO, callback);
   }
  void cancel();
  bool get isActive;
  external static Timer _createTimer(Duration duration, void callback());
  external static Timer _createPeriodicTimer(Duration duration, void callback(Timer timer));
 }
- typedef void __CastType81(Timer __u82);
+ typedef void __CastType76(Timer __u77);