Roll Observatory packages and add a roll script

packages/charted/lib/selection/src/transition_impl.dart

 /*
  * Copyright 2014 Google Inc. All rights reserved.
  *
  * Use of this source code is governed by a BSD-style
  * license that can be found in the LICENSE file or at
  * https://developers.google.com/open-source/licenses/bsd
  */
 part of charted.selection.transition;
 
 // handle transitions on an element-basis, so we can cancel if another is
@@ skipping 178 matching lines @@
     var t = new _TransitionImpl(_selection, delay);
     t.ease = ease;
     t.durationWithCallback(_duration);
     return t;
   }
 
   void remove() {
     _remove = true;
   }
 }