cps-ir: Register IndexSet calls like other calls in JS codegen.

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 237 matching lines @@
   }
 
   void registerMethodInvoke(tree_ir.InvokeMethod node) {
     Selector selector = node.selector;
     if (selector.isGetter) {
       registry.registerDynamicGetter(selector);
     } else if (selector.isSetter) {
       registry.registerDynamicSetter(selector);
     } else {
       assert(invariant(CURRENT_ELEMENT_SPANNABLE,
-          selector.isCall || selector.isOperator || selector.isIndex,
+          selector.isCall || selector.isOperator ||
+          selector.isIndex || selector.isIndexSet,
           message: 'unexpected kind ${selector.kind}'));
       // TODO(sigurdm): We should find a better place to register the call.
       Selector call = new Selector.callClosureFrom(selector);
       registry.registerDynamicInvocation(call);
       registry.registerDynamicInvocation(selector);
     }
   }
 
   @override
   js.Expression visitInvokeMethod(tree_ir.InvokeMethod node) {
@@ skipping 354 matching lines @@
 
   @override
   visitFunctionDeclaration(tree_ir.FunctionDeclaration node) {
     return errorUnsupportedNode(node);
   }
 
   errorUnsupportedNode(tree_ir.DartSpecificNode node) {
     throw "Unsupported node in JS backend: $node";
   }
 }