Support doubles in observatory.

runtime/bin/vmservice/client/lib/src/elements/observatory_element.dart

 // Copyright (c) 2013, 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.
 
 library observatory_element;
 
 import 'dart:math';
 import 'package:polymer/polymer.dart';
 
 /// Base class for all Observatory custom elements.
@@ skipping 106 matching lines @@
   }
 
   bool isInstance(String type) {
     return type == 'Instance';
   }
 
   bool isClosure(String type) {
     return type == 'Closure';
   }
 
+  bool isDouble(String type) {
+    return type == 'Double';
+  }
+
   bool isList(String type) {
     return (type == 'GrowableObjectArray' ||
             type == 'Array');
   }
 
   bool isUnexpected(String type) {
     return (!['Null',
               'Smi',
               'Mint',
               'Biginit',
               'Bool',
               'String',
               'Closure',
+              'Double',
               'Instance',
               'GrowableObjectArray',
               'Array',
               'Error'].contains(type));
   }
 }