Remove holders for runtime type information.

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 1506 matching lines @@
   }
 
   void addedDynamicSetter(Selector setter, HType type) {
     fieldTypes.addedDynamicSetter(setter, type);
   }
 
   HType optimisticFieldType(Element element) {
     return fieldTypes.optimisticFieldType(element);
   }
 
+  Element getImplementationClass(Element element) {
+    if (element == compiler.intClass) {
+      return jsIntClass;
+    } else if (element == compiler.boolClass) {
+      return jsBoolClass;
+    } else if (element == compiler.numClass) {
+      return jsNumberClass;
+    } else if (element == compiler.doubleClass) {
+      return jsDoubleClass;
+    } else if (element == compiler.stringClass) {
+      return jsStringClass;
+    } else if (element == compiler.listClass) {
+      return jsArrayClass;
+    } else {
+      return element;
+    }
+  }
+
   /**
    * Returns the checked mode helper that will be needed to do a type check/type
    * cast on [type] at runtime. Note that this method is being called both by
    * the resolver with interface types (int, String, ...), and by the SSA
    * backend with implementation types (JSInt, JSString, ...).
    */
   Element getCheckedModeHelper(DartType type, {bool typeCast}) {
     return compiler.findHelper(getCheckedModeHelperName(
         type, typeCast: typeCast, nativeCheckOnly: false));
   }
@@ skipping 238 matching lines @@
   ClassElement get constListImplementation => jsArrayClass;
   ClassElement get fixedListImplementation => jsFixedArrayClass;
   ClassElement get growableListImplementation => jsExtendableArrayClass;
   ClassElement get mapImplementation => mapLiteralClass;
   ClassElement get constMapImplementation => constMapLiteralClass;
   ClassElement get functionImplementation => jsFunctionClass;
   ClassElement get typeImplementation => typeLiteralClass;
   ClassElement get boolImplementation => jsBoolClass;
   ClassElement get nullImplementation => jsNullClass;
 }