Add *IndexSetIfNull methods to SemanticSendVisitor.

tests/compiler/dart2js/semantic_visitor_test_send_visitor.dart

 // Copyright (c) 2015, 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.
 
 part of dart2js.semantics_visitor_test;
 
 class SemanticSendTestVisitor extends SemanticTestVisitor {
 
   SemanticSendTestVisitor(TreeElements elements) : super(elements);
 
@@ skipping 3533 matching lines @@
       MethodElement getter,
       Element element,
       Node rhs,
       arg) {
     visits.add(new Visit(
         VisitKind.VISIT_UNRESOLVED_TOP_LEVEL_SETTER_SET_IF_NULL,
         getter: getter, rhs: rhs));
     super.visitUnresolvedTopLevelSetterSetIfNull(
         node, getter, element, rhs, arg);
   }
+
+  @override
+  visitIndexSetIfNull(
+      SendSet node,
+      Node receiver,
+      Node index,
+      Node rhs,
+      arg) {
+    visits.add(new Visit(
+        VisitKind.VISIT_INDEX_SET_IF_NULL,
+        receiver: receiver, index: index, rhs: rhs));
+    super.visitIndexSetIfNull(node, receiver, index, rhs, arg);
+  }
+
+  @override
+  visitSuperIndexSetIfNull(
+      SendSet node,
+      MethodElement getter,
+      MethodElement setter,
+      Node index,
+      Node rhs,
+      arg) {
+    visits.add(new Visit(
+        VisitKind.VISIT_SUPER_INDEX_SET_IF_NULL,
+        getter: getter, setter: setter, index: index, rhs: rhs));
+    super.visitSuperIndexSetIfNull(node, getter, setter, index, rhs, arg);
+  }
+
+  @override
+  visitUnresolvedSuperGetterIndexSetIfNull(
+      Send node,
+      Element element,
+      MethodElement setter,
+      Node index,
+      Node rhs,
+      arg) {
+    visits.add(new Visit(
+        VisitKind.VISIT_UNRESOLVED_SUPER_GETTER_INDEX_SET_IF_NULL,
+        setter: setter, index: index, rhs: rhs));
+    super.visitUnresolvedSuperGetterIndexSetIfNull(
+        node, element, setter, index, rhs, arg);
+  }
+
+  @override
+  visitUnresolvedSuperSetterIndexSetIfNull(
+      Send node,
+      MethodElement getter,
+      Element element,
+      Node index,
+      Node rhs,
+      arg) {
+    visits.add(new Visit(
+        VisitKind.VISIT_UNRESOLVED_SUPER_SETTER_INDEX_SET_IF_NULL,
+        getter: getter, index: index, rhs: rhs));
+    super.visitUnresolvedSuperSetterIndexSetIfNull(
+        node, getter, element, index, rhs, arg);
+  }
+
+  @override
+  visitUnresolvedSuperIndexSetIfNull(
+      Send node,
+      Element element,
+      Node index,
+      Node rhs,
+      arg) {
+    visits.add(new Visit(
+        VisitKind.VISIT_UNRESOLVED_SUPER_INDEX_SET_IF_NULL,
+        index: index, rhs: rhs));
+    super.visitUnresolvedSuperIndexSetIfNull(node, element, index, rhs, arg);
+  }
+
+  @override
+  errorInvalidIndexSetIfNull(
+      SendSet node,
+      ErroneousElement error,
+      Node index,
+      Node rhs,
+      arg) {
+    visits.add(new Visit(
+        VisitKind.ERROR_INVALID_SET_IF_NULL,
+        index: index, rhs: rhs));
+    super.visitUnresolvedSuperIndexSetIfNull(node, error, index, rhs, arg);
+  }
 }