Supported versioned patching.

pkg/compiler/lib/src/js_backend/backend.dart

 // Copyright (c) 2012, 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 js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 const bool USE_CPS_IR = const bool.fromEnvironment("USE_CPS_IR");
 
@@ skipping 73 matching lines @@
 
   /// The list of functions for classes in the [internalLibrary] that we want
   /// to inline always.  Any function in this list must be inlinable with
   /// respect to the conditions used in [InlineWeeder.canInline], except for
   /// size/complexity heuristics.
   static const Map<String, List<String>> ALWAYS_INLINE =
       const <String, List<String>> {
     'IterableMixinWorkaround': const <String>['forEach'],
   };
 
+  String get patchVersion => USE_NEW_EMITTER ? 'new' : 'old';
+
   /// List of [FunctionElement]s that we want to inline always.  This list is
   /// filled when resolution is complete by looking up in [internalLibrary].
   List<FunctionElement> functionsToAlwaysInline;
 
   /// Reference to the internal library to lookup functions to always inline.
   LibraryElement internalLibrary;
 
 
   /// Set of classes that need to be considered for reflection although not
   /// otherwise visible during resolution.
@@ skipping 2423 matching lines @@
   }
 }
 
 /// Records that [constant] is used by the element behind [registry].
 class Dependency {
   final ConstantValue constant;
   final Element annotatedElement;
 
   const Dependency(this.constant, this.annotatedElement);
 }