Move the handling of operator[] into the new interceptors.

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

 // Copyright (c) 2012, 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 js_backend;
 
 typedef void Recompile(Element element);
 
 class ReturnInfo {
   HType returnType;
@@ skipping 817 matching lines @@
   void registerInstantiatedClass(ClassElement cls, Enqueuer enqueuer) {
     ClassElement result = null;
     if (!_interceptorsAreInitialized) {
       initializeInterceptorElements();
       _interceptorsAreInitialized = true;
     }
     if (cls == compiler.stringClass) {
       result = jsStringClass;
     } else if (cls == compiler.listClass) {
       result = jsArrayClass;
+      // The backend will try to optimize array access and use the
+      // [:ioore:] and [:iae:] helpers directly.
+      enqueuer.registerStaticUse(
+          compiler.findHelper(const SourceString('ioore')));
+      enqueuer.registerStaticUse(
+          compiler.findHelper(const SourceString('iae')));
     } else if (cls == compiler.intClass) {
       result = jsIntClass;
       enqueuer.registerInstantiatedClass(jsNumberClass);
     } else if (cls == compiler.doubleClass) {
       result = jsDoubleClass;
       enqueuer.registerInstantiatedClass(jsNumberClass);
     } else if (cls == compiler.functionClass) {
       result = jsFunctionClass;
     } else if (cls == compiler.boolClass) {
       result = jsBoolClass;
@@ skipping 268 matching lines @@
     print("Inferred return types:");
     print("----------------------");
     dumpReturnTypes();
     print("");
     print("Inferred field types:");
     print("------------------------");
     fieldTypes.dump();
     print("");
   }
 }