fix truncate call to use extension method

lib/runtime/dart/core.js

 dart_library.library('dart/core', null, /* Imports */[
   "dart_runtime/dart"
 ], /* Lazy imports */[
   'dart/_js_helper',
   'dart/_internal',
   'dart/collection',
   'dart/_interceptors',
   'dart/convert'
 ], function(exports, dart, _js_helper, _internal, collection, _interceptors, convert) {
   'use strict';
@@ skipping 465 matching lines @@
     }
     ['-'](other) {
       return new Duration._microseconds(dart.notNull(this[_duration]) - dart.notNull(other[_duration]));
     }
     ['*'](factor) {
       return new Duration._microseconds((dart.notNull(this[_duration]) * dart.notNull(factor))[dartx.round]());
     }
     ['~/'](quotient) {
       if (quotient == 0)
         dart.throw(new IntegerDivisionByZeroException());
-      return new Duration._microseconds((dart.notNull(this[_duration]) / dart.notNull(quotient)).truncate());
+      return new Duration._microseconds((dart.notNull(this[_duration]) / dart.notNull(quotient))[dartx.truncate]());
     }
     ['<'](other) {
       return dart.notNull(this[_duration]) < dart.notNull(other[_duration]);
     }
     ['>'](other) {
       return dart.notNull(this[_duration]) > dart.notNull(other[_duration]);
     }
     ['<='](other) {
       return dart.notNull(this[_duration]) <= dart.notNull(other[_duration]);
     }
     ['>='](other) {
       return dart.notNull(this[_duration]) >= dart.notNull(other[_duration]);
     }
     get inDays() {
-      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_DAY)).truncate();
+      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_DAY))[dartx.truncate]();
     }
     get inHours() {
-      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_HOUR)).truncate();
+      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_HOUR))[dartx.truncate]();
     }
     get inMinutes() {
-      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_MINUTE)).truncate();
+      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_MINUTE))[dartx.truncate]();
     }
     get inSeconds() {
-      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_SECOND)).truncate();
+      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_SECOND))[dartx.truncate]();
     }
     get inMilliseconds() {
-      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_MILLISECOND)).truncate();
+      return (dart.notNull(this[_duration]) / dart.notNull(Duration.MICROSECONDS_PER_MILLISECOND))[dartx.truncate]();
     }
     get inMicroseconds() {
       return this[_duration];
     }
     ['=='](other) {
       if (!dart.is(other, Duration))
         return false;
       return dart.equals(this[_duration], dart.dload(other, _duration));
     }
     get hashCode() {
@@ skipping 1073 matching lines @@
     get elapsedTicks() {
       if (this[_start] == null) {
         return 0;
       }
       return this[_stop] == null ? dart.notNull(Stopwatch._now()) - dart.notNull(this[_start]) : dart.notNull(this[_stop]) - dart.notNull(this[_start]);
     }
     get elapsed() {
       return new Duration({microseconds: this.elapsedMicroseconds});
     }
     get elapsedMicroseconds() {
-      return (dart.notNull(this.elapsedTicks) * 1000000 / dart.notNull(this.frequency)).truncate();
+      return (dart.notNull(this.elapsedTicks) * 1000000 / dart.notNull(this.frequency))[dartx.truncate]();
     }
     get elapsedMilliseconds() {
-      return (dart.notNull(this.elapsedTicks) * 1000 / dart.notNull(this.frequency)).truncate();
+      return (dart.notNull(this.elapsedTicks) * 1000 / dart.notNull(this.frequency))[dartx.truncate]();
     }
     get isRunning() {
       return this[_start] != null && this[_stop] == null;
     }
     static _initTicker() {
       _js_helper.Primitives.initTicker();
       Stopwatch._frequency = _js_helper.Primitives.timerFrequency;
     }
     static _now() {
       return dart.as(dart.dcall(_js_helper.Primitives.timerTicks), int);
@@ skipping 1744 matching lines @@
   exports.StackTrace = StackTrace;
   exports.Stopwatch = Stopwatch;
   exports.String = String;
   exports.RuneIterator = RuneIterator;
   exports.StringBuffer = StringBuffer;
   exports.StringSink = StringSink;
   exports.Symbol = Symbol;
   exports.Type = Type;
   exports.Uri = Uri;
 });