Implement references to "this" in the new IR.

sdk/lib/_internal/compiler/implementation/ir/ir_nodes.dart

 // Copyright (c) 2013, 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.
 
 // IrNodes are kept in a separate library to have precise control over their
 // dependencies on other parts of the system.
 library dart2js.ir_nodes;
 
 import '../dart2jslib.dart' as dart2js show Constant, ConstructedConstant;
 import '../elements/elements.dart'
@@ skipping 289 matching lines @@
 class Constant extends Primitive {
   final dart2js.Constant value;
 
   Constant(this.value);
 
   dart2js.Constant get constant => value;
 
   accept(Visitor visitor) => visitor.visitConstant(this);
 }
 
+class This extends Primitive {
+  This();
+
+  accept(Visitor visitor) => visitor.visitThis(this);
+}
+
 class LiteralList extends Primitive {
   /// The List type being created; this is not the type argument.
   final GenericType type;
   final List<Reference> values;
 
   /// Set to null if this is not a const literal list.
   final dart2js.Constant constant;
 
   LiteralList(this.type, List<Primitive> values, [this.constant])
       : this.values = _referenceList(values);
@@ skipping 79 matching lines @@
   T visitInvokeContinuation(InvokeContinuation node) => visitExpression(node);
   T visitInvokeMethod(InvokeMethod node) => visitExpression(node);
   T visitInvokeConstructor(InvokeConstructor node) => visitExpression(node);
   T visitConcatenateStrings(ConcatenateStrings node) => visitExpression(node);
   T visitBranch(Branch node) => visitExpression(node);
 
   // Definitions.
   T visitLiteralList(LiteralList node) => visitPrimitive(node);
   T visitLiteralMap(LiteralMap node) => visitPrimitive(node);
   T visitConstant(Constant node) => visitPrimitive(node);
+  T visitThis(This node) => visitPrimitive(node);
   T visitInvokeConstConstructor(InvokeConstConstructor node) => visitPrimitive(node);
   T visitParameter(Parameter node) => visitPrimitive(node);
   T visitContinuation(Continuation node) => visitDefinition(node);
 
   // Conditions.
   T visitIsTrue(IsTrue node) => visitCondition(node);
 }
 
 /// Generate a Lisp-like S-expression representation of an IR node as a string.
 /// The representation is not pretty-printed, but it can easily be quoted and
@@ skipping 255 matching lines @@
     for (int i = node.parameters.length - 1; i >= 0; --i) {
       release(node.parameters[i]);
     }
   }
 
   void visitIsTrue(IsTrue node) {
     visitReference(node.value);
   }
 
 }