Use closure conversion in new dart2js backend.

pkg/compiler/lib/src/tree_ir/tree_ir_builder.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.
 
 library tree_ir_builder;
 
 import '../dart2jslib.dart' as dart2js;
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
@@ skipping 29 matching lines @@
  * control-flow recognition.
  *
  * Otherwise, the output of Builder looks very much like the input.  In
  * particular, intermediate values and blocks used for local control flow are
  * still all named.
  */
 class Builder extends cps_ir.Visitor<Node> {
   final dart2js.InternalErrorFunction internalError;
 
   /// Maps variable/parameter elements to the Tree variables that represent it.
-  final Map<Element, List<Variable>> element2variables =
-      <Element,List<Variable>>{};
+  final Map<Local, List<Variable>> local2variables = <Local, List<Variable>>{};
 
-  /// Like [element2variables], except for closure variables.
+  /// Like [local2variables], except for closure variables.
   final Map<cps_ir.ClosureVariable, Variable> local2closure =
       <cps_ir.ClosureVariable, Variable>{};
 
   // Continuations with more than one use are replaced with Tree labels.  This
   // is the mapping from continuations to labels.
   final Map<cps_ir.Continuation, Label> labels = <cps_ir.Continuation, Label>{};
 
   ExecutableElement currentElement;
   cps_ir.Continuation returnContinuation;
 
@@ skipping 16 matching lines @@
     return local2closure.putIfAbsent(irVariable,
         () => new Variable(currentElement, irVariable.hint));
   }
 
   /// Obtains the variable representing the given primitive. Returns null for
   /// primitives that have no reference and do not need a variable.
   Variable getVariable(cps_ir.Primitive primitive) {
     if (primitive.registerIndex == null) {
       return null; // variable is unused
     }
-    List<Variable> variables = element2variables.putIfAbsent(primitive.hint,
+    List<Variable> variables = local2variables.putIfAbsent(primitive.hint,
         () => <Variable>[]);
     while (variables.length <= primitive.registerIndex) {
       variables.add(new Variable(currentElement, primitive.hint));
     }
     return variables[primitive.registerIndex];
   }
 
   /// Obtains a reference to the tree Variable corresponding to the IR primitive
   /// referred to by [reference].
   /// This increments the reference count for the given variable, so the
@@ skipping 444 matching lines @@
     // visited.
     internalError(CURRENT_ELEMENT_SPANNABLE, 'Unexpected IR node: $node.');
     return null;
   }
 
   Expression visitIsTrue(cps_ir.IsTrue node) {
     return getVariableReference(node.value);
   }
 }