dart2js cps: Keep interceptors in a separate field.

pkg/compiler/lib/src/cps_ir/backward_null_check_remover.dart

 library dart2js.cps_ir.backward_null_check_remover;
 
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
 import '../common/names.dart';
 import '../universe/selector.dart';
 import 'type_mask_system.dart';
 import 'cps_fragment.dart';
 
 /// Removes null checks that are follwed by another instruction that will
@@ skipping 41 matching lines @@
 
   /// Returns an operand of [prim] that throws if null is passed into it.
   Primitive getNullCheckedOperand(Primitive prim) {
     if (prim is ReceiverCheck) return prim.value;
     if (prim is GetLength) return prim.object;
     if (prim is GetField) return prim.object;
     if (prim is GetIndex) return prim.object;
     if (prim is SetField) return prim.object;
     if (prim is SetIndex) return prim.object;
     if (prim is InvokeMethod && !selectorsOnNull.contains(prim.selector)) {
-      return prim.dartReceiver;
+      return prim.receiver;
     }
     if (prim is ForeignCode) {
       return prim.isNullGuardOnNullFirstArgument() ? prim.argument(0) : null;
     }
     return null;
   }
 
   /// It has been determined that the null check in [prim] made redundant by
   /// [newNullCheck].  Eliminate [prim] if it is not needed any more.
   void tryEliminateRedundantNullCheck(Primitive prim, Primitive newNullCheck) {
@@ skipping 46 matching lines @@
   void visitLetHandler(LetHandler node) {
     nullCheckedValue = null;
   }
 
   visitInvokeContinuation(InvokeContinuation node) {
     if (!node.isRecursive) {
       nullCheckedValue = nullCheckedValueAt[node.continuation];
     }
   }
 }