dart2js: support tear-offs in the startup emitter.

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;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 224 matching lines @@
       new Uri(scheme: 'dart', path: '_js_embedded_names');
   static final Uri DART_ISOLATE_HELPER =
       new Uri(scheme: 'dart', path: '_isolate_helper');
   static final Uri DART_HTML =
       new Uri(scheme: 'dart', path: 'html');
 
   static const String INVOKE_ON = '_getCachedInvocation';
   static const String START_ROOT_ISOLATE = 'startRootIsolate';
 
 
+  String get patchVersion => emitter.patchVersion;
+  
   bool get supportsReflection => emitter.emitter.supportsReflection;
 
-  String get patchVersion => USE_LAZY_EMITTER ? 'lazy' : 'full';
-
   final Annotations annotations;
 
   /// 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.
   Iterable<ClassElement> get classesRequiredForReflection {
     // TODO(herhut): Clean this up when classes needed for rti are tracked.
@@ skipping 2752 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);
 }