Roll Observatory packages and add a roll script

packages/quiver/lib/mirrors.dart

 // Copyright 2013 Google Inc. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 70 matching lines @@
       if (i.namedArguments != null && i.namedArguments.isNotEmpty) {
         // this will fail until named argument support is implemented
         return mirror.invoke(
             symbol, i.positionalArguments, i.namedArguments).reflectee;
       }
       return mirror.invoke(symbol, i.positionalArguments).reflectee;
     }
     return super.noSuchMethod(i);
   }
 }