dart2js cps: Always use interceptors and type tags for 'is' checks.

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 1637 matching lines @@
         element == compiler.numClass ||
         element == compiler.intClass ||
         element == compiler.doubleClass ||
         element == jsArrayClass ||
         element == jsMutableArrayClass ||
         element == jsExtendableArrayClass ||
         element == jsFixedArrayClass ||
         element == jsUnmodifiableArrayClass;
   }
 
-  /// Return [true] if the class is represented by a native JavaSCript type in
-  /// the generated code.
-  bool isNativePrimitiveType(ClassElement cls ) {
-    // TODO(karlklose): cleanup/merge with hasDirectCheck, when the rest of the
-    // checks are implemented in the CPS IR.
-    return cls == compiler.intClass ||
-        cls == compiler.numClass ||
-        cls == compiler.doubleClass ||
-        cls == compiler.boolClass ||
-        cls == compiler.stringClass;
-  }
-
   bool mayGenerateInstanceofCheck(DartType type) {
     // We can use an instanceof check for raw types that have no subclass that
     // is mixed-in or in an implements clause.
 
     if (!type.isRaw) return false;
     ClassElement classElement = type.element;
     if (isInterceptorClass(classElement)) return false;
     return compiler.world.hasOnlySubclasses(classElement);
   }
 
@@ skipping 1261 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);
 }