Patches to support Dart VM patch files in dart2js.

sdk/lib/developer/profiler.dart

 // Copyright (c) 2014, 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.developer;
 
 /// A UserTag can be used to group samples in the Observatory profiler.
 abstract class UserTag {
   /// The maximum number of UserTag instances that can be created by a program.
   static const MAX_USER_TAGS = 64;
 
-  factory UserTag(String label) => new _FakeUserTag(label);
+  external factory UserTag(String label);
 
   /// Label of [this].
   String get label;
 
   /// Make [this] the current tag for the isolate. Returns the current tag
   /// before setting.
   UserTag makeCurrent();
 
   /// The default [UserTag] with label 'Default'.
-  static UserTag get defaultTag => _FakeUserTag._defaultTag;
+  external static UserTag get defaultTag;
 }
 
 // This is a fake implementation of UserTag so that code can compile and run
 // in dart2js.
 class _FakeUserTag implements UserTag {
   static Map _instances = {};
 
   _FakeUserTag.real(this.label);
 
   factory _FakeUserTag(String label) {
@@ skipping 20 matching lines @@
     _currentTag = this;
     return old;
   }
 
   static final UserTag _defaultTag = new _FakeUserTag('Default');
 }
 
 var _currentTag = _FakeUserTag._defaultTag;
 
 /// Returns the current [UserTag] for the isolate.
-UserTag getCurrentTag() {
-  return _currentTag;
-}
+external UserTag getCurrentTag();
 
 /// Abstract [Metric] class. Metric names must be unique, are hierarchical,
 /// and use periods as separators. For example, 'a.b.c'. Uniqueness is only
 /// enforced when a Metric is registered. The name of a metric cannot contain
 /// the slash ('/') character.
 abstract class Metric {
   /// [name] of this metric.
   final String name;
   /// [description] of this metric.
   final String description;
@@ skipping 112 matching lines @@
     for (var metric in _metrics.values) {
       metrics.add(metric._toJSON());
     }
     var map = {
       'type': 'MetricList',
       'metrics': metrics,
     };
     return JSON.encode(map);
   }
 }