Let operator* in Duration accept doubles.

sdk/lib/core/duration.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.core;
 
 /**
  * A [Duration] represents a time span. A duration can be negative.
  */
 class Duration implements Comparable<Duration> {
@@ skipping 38 matching lines @@
    * is allowed to have a value greater than 23.
    *
    * All individual parts are allowed to be negative.
    * All arguments are by default 0.
    */
   const Duration({int days: 0,
                   int hours: 0,
                   int minutes: 0,
                   int seconds: 0,
                   int milliseconds: 0,
-                  int microseconds: 0})
+                  int microseconds: 0}) 

[floitsch, 2013/06/25 15:28:02]

Remove trailing space.

[zarah, 2013/06/25 15:54:05]

Done.

       : _duration = days * MICROSECONDS_PER_DAY +
                     hours * MICROSECONDS_PER_HOUR +
                     minutes * MICROSECONDS_PER_MINUTE +
                     seconds * MICROSECONDS_PER_SECOND +
                     milliseconds * MICROSECONDS_PER_MILLISECOND +
                     microseconds;
 
   /**
    * Returns the sum of this [Duration] and [other]  as a new [Duration].
    */
   Duration operator +(Duration other) {
     return new Duration(microseconds: _duration + other._duration);
   }
 
   /**
    * Returns the difference of this [Duration] and [other] as a new
    * [Duration].
    */
   Duration operator -(Duration other) {
     return new Duration(microseconds: _duration - other._duration);
   }
 
   /**
    * Multiplies this [Duration] by the given [factor] and returns the result
    * as a new [Duration].
+   *
+   * Note when [factor] is a double, and the duration is greater than

[floitsch, 2013/06/25 15:28:02]

Note that ...
or:
Note: ...

[zarah, 2013/06/25 15:54:05]

Done.

+   * 53 bits, precision is lost because of double-precision arithmetic. 
    */
-  Duration operator *(int factor) {
-    return new Duration(microseconds: _duration * factor);
+  Duration operator *(num factor) {
+    return new Duration(microseconds: (_duration * factor).round());
   }
 
   /**
    * Divides this [Duration] by the given [quotient] and returns the truncated
    * result as a new [Duration].
    *
    * Throws an [IntegerDivisionByZeroException] if [quotient] is `0`.
    */
   Duration operator ~/(int quotient) {
     // By doing the check here instead of relying on "~/" below we get the
@@ skipping 76 matching lines @@
           new Duration(microseconds: -inMicroseconds);
       return "-$duration";
     }
     String twoDigitMinutes = twoDigits(inMinutes.remainder(MINUTES_PER_HOUR));
     String twoDigitSeconds = twoDigits(inSeconds.remainder(SECONDS_PER_MINUTE));
     String sixDigitUs =
         sixDigits(inMicroseconds.remainder(MICROSECONDS_PER_SECOND));
     return "$inHours:$twoDigitMinutes:$twoDigitSeconds.$sixDigitUs";
   }
 }