Generate tear-off closures dynamically.

dart/sdk/lib/_internal/compiler/implementation/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;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked;
 
   JavaScriptItemCompilationContext()
@@ skipping 824 matching lines @@
         // of the map.
         enqueueClass(enqueuer, compiler.listClass, elements);
         enqueueClass(enqueuer, mapLiteralClass, elements);
         enqueueInResolution(getMapMaker(), elements);
       } else if (cls == compiler.boundClosureClass) {
         // TODO(ngeoffray): Move the bound closure class in the
         // backend.
         enqueueClass(enqueuer, compiler.boundClosureClass, elements);
       }
     }
+    if (cls == compiler.closureClass) {
+      enqueue(enqueuer,
+              compiler.findHelper(const SourceString('closureFromTearOff')),
+              elements);
+    }
     ClassElement result = null;
     if (cls == compiler.stringClass || cls == jsStringClass) {
       addInterceptors(jsStringClass, enqueuer, elements);
     } else if (cls == compiler.listClass
                || cls == jsArrayClass
                || cls == jsFixedArrayClass
                || cls == jsExtendableArrayClass) {
       addInterceptors(jsArrayClass, enqueuer, elements);
       addInterceptors(jsMutableArrayClass, enqueuer, elements);
       addInterceptors(jsFixedArrayClass, enqueuer, elements);
@@ skipping 1044 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }