dart2js cps: Set a flag on InvokeMethod when the receiver is intercepted

pkg/compiler/lib/src/cps_ir/cps_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.
 library dart2js.ir_nodes;
 
 import 'dart:collection';
 import '../constants/values.dart' as values;
 import '../dart_types.dart' show DartType, InterfaceType, TypeVariableType;
 import '../elements/elements.dart';
 import '../io/source_information.dart' show SourceInformation;
@@ skipping 387 matching lines @@
 /// The [selector] records the names of named arguments. The value of named
 /// arguments occur at the end of the [arguments] list, in normalized order.
 class InvokeMethod extends CallExpression {
   Reference<Primitive> receiver;
   Selector selector;
   TypeMask mask;
   final List<Reference<Primitive>> arguments;
   final Reference<Continuation> continuation;
   final SourceInformation sourceInformation;
 
+  /// If true, the [receiver] is intercepted and the actual receiver is in
+  /// the first argument. Otherwise, the [receiver] is the actual receiver.
+  ///
+  /// This flag is always false for non-intercepted selectors, but it may also
+  /// be false for intercepted selectors after dummy receiver optimization
+  /// (in this case the first argument is a dummy value).
+  ///
+  /// It is always false before the unsugaring pass, where interceptors have
+  /// not yet been introduced.
+  bool receiverIsIntercepted = false;
+
   /// If true, it is known that the receiver cannot be `null`.
   bool receiverIsNotNull = false;
 
   InvokeMethod(Primitive receiver,
                this.selector,
                this.mask,
                List<Primitive> arguments,
                Continuation continuation,
                [this.sourceInformation])
       : this.receiver = new Reference<Primitive>(receiver),
@@ skipping 1315 matching lines @@
 /// Visit a just-deleted subterm and unlink all [Reference]s in it.
 class RemovalVisitor extends RecursiveVisitor {
   processReference(Reference reference) {
     reference.unlink();
   }
 
   static void remove(Node node) {
     (new RemovalVisitor()).visit(node);
   }
 }