dart2js cps: Use more precise type inference for direct index access.

pkg/compiler/lib/src/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;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 314 matching lines @@
   ClassElement noSideEffectsClass;
   ClassElement noThrowsClass;
   ClassElement noInlineClass;
   ClassElement forceInlineClass;
   ClassElement irRepresentationClass;
 
   Element getInterceptorMethod;
 
   ClassElement jsInvocationMirrorClass;
 
+  ClassElement typedArrayClass;
+  ClassElement typedArrayOfIntClass;
+
   /// If [true], the compiler will emit code that logs whenever a method is
   /// called. When TRACE_METHOD is 'console' this will be logged
   /// directly in the JavaScript console. When TRACE_METHOD is 'post' the
   /// information will be sent to a server via a POST request.
   static const String TRACE_METHOD = const String.fromEnvironment('traceCalls');
   static const bool TRACE_CALLS =
     TRACE_METHOD == 'post' || TRACE_METHOD == 'console';
   Element traceHelper;
 
   TypeMask get stringType => compiler.typesTask.stringType;
@@ skipping 1803 matching lines @@
         preserveLibraryNamesMarker = find(library, 'preserveLibraryNames');
       } else if (uri == DART_JS_NAMES) {
         preserveNamesMarker = find(library, 'preserveNames');
       } else if (uri == DART_EMBEDDED_NAMES) {
         jsGetNameEnum = find(library, 'JsGetName');
         jsBuiltinEnum = find(library, 'JsBuiltin');
       } else if (uri == Uris.dart_html) {
         htmlLibraryIsLoaded = true;
       } else if (uri == PACKAGE_LOOKUP_MAP) {
         lookupMapAnalysis.init(library);
+      } else if (uri == Uris.dart__native_typed_data) {
+        typedArrayClass = findClass('NativeTypedArray');
+        typedArrayOfIntClass = findClass('NativeTypedArrayOfInt');
       }
       annotations.onLibraryScanned(library);
     });
   }
 
   Future onLibrariesLoaded(LoadedLibraries loadedLibraries) {
     if (!loadedLibraries.containsLibrary(Uris.dart_core)) {
       return new Future.value();
     }
 
@@ skipping 992 matching lines @@
   }
 }
 
 /// Records that [constant] is used by the element behind [registry].
 class Dependency {
   final ConstantValue constant;
   final Element annotatedElement;
 
   const Dependency(this.constant, this.annotatedElement);
 }