Use closure conversion in new dart2js backend.

pkg/compiler/lib/src/js_emitter/code_emitter_task.dart

Index: pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
diff --git a/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart b/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
index a027ced641dbe594cc11f9e4fbb62976e4dc41cd..db3400009dfc64190d1fc968b1f73c5258b006b4 100644
--- a/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
+++ b/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
@@ -120,6 +120,10 @@ class CodeEmitterTask extends CompilerTask {
     return emitter.typeAccess(e);
   }
 
+  jsAst.Expression closureClassConstructorAccess(ClosureClassElement e) {
+    return emitter.closureClassConstructorAccess(e);
+  }
+
   void registerReadTypeVariable(TypeVariableElement element) {
     readTypeVariables.add(element);
   }
@@ -458,6 +462,9 @@ abstract class Emitter {
   /// Returns the JS expression representing the type [e].
   jsAst.Expression typeAccess(Element e);
 
+  /// Returns the JS constructor for the given closure class [e].
+  jsAst.Expression closureClassConstructorAccess(ClosureClassElement e);
+
   int compareConstants(ConstantValue a, ConstantValue b);
   bool isConstantInlinedOrAlreadyEmitted(ConstantValue constant);