Remove unused code

pkg/compiler/lib/src/js_backend/codegen/codegen.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 code_generator;
 
 import 'glue.dart';
 
 import '../../tree_ir/tree_ir_nodes.dart' as tree_ir;
 import '../../js/js.dart' as js;
@@ skipping 200 matching lines @@
 
   @override
   js.Expression visitTypeOperator(tree_ir.TypeOperator node) {
     return giveup(node);
     // TODO: implement visitTypeOperator
   }
 
   @override
   js.Expression visitVariable(tree_ir.Variable node) {
     return new js.VariableUse(getVariableName(node));
-    // TODO: implement visitVariable
   }
 
   @override
   void visitContinue(tree_ir.Continue node) {
     return giveup(node);
     // TODO: implement visitContinue
   }
 
   @override
   void visitExpressionStatement(tree_ir.ExpressionStatement node) {
@@ skipping 15 matching lines @@
   }
 
   @override
   void visitLabeledStatement(tree_ir.LabeledStatement node) {
     giveup(node);
     // TODO: implement visitLabeledStatement
   }
 
   @override
   void visitAssign(tree_ir.Assign node) {
-
-    bool isFirstOccurrence = (variableNames[node.variable] == null);
-    bool isDeclaredHere = node.variable.host.element == currentFunction;
-    String name = getVariableName(node.variable);
     tree_ir.Expression value = node.definition;
     js.Expression definition = visitExpression(value);
 
     accumulator.add(new js.ExpressionStatement(new js.Assignment(
         visitVariable(node.variable),
         definition)));
     visitStatement(node.next);
   }
 
   @override
@@ skipping 15 matching lines @@
   }
 
   @override
   void visitReturn(tree_ir.Return node) {
     accumulator.add(new js.Return(visitExpression(node.value)));
   }
 
   bool isNullLiteral(js.Expression exp) => exp is js.LiteralNull;
 
 }