Add a native subtype of function that uses the native C++ class hierarchy to check if an element

Source/bindings/dart/DartDOMWrapper.h

Index: Source/bindings/dart/DartDOMWrapper.h
===================================================================
--- Source/bindings/dart/DartDOMWrapper.h	(revision 1437)
+++ Source/bindings/dart/DartDOMWrapper.h	(working copy)
@@ -30,6 +30,8 @@
 #ifndef DartDOMWrapper_h
 #define DartDOMWrapper_h
 
+#include "DartWebkitClassIds.h"
+
 #include "bindings/dart/DartDOMData.h"
 #include "bindings/dart/DartExceptionState.h"
 #include "bindings/dart/DartUtilities.h"
@@ -101,7 +103,7 @@
         Dart_PersistentHandle type = dartClass(domData, className, libraryId, cid);
         ASSERT(!Dart_IsError(type));
         Dart_Handle wrapper = Dart_Allocate(type);
-        writeNativePointer(wrapper, kNativeImplementationIndex, domObject);
+        writeNativePointer(wrapper, domObject, cid);
         associateWrapper<BindingsClass>(domData, domObject, wrapper);
         return wrapper;
     }
@@ -142,14 +144,14 @@
         if (Dart_IsNull(wrapper))
             return 0;
 
-        // FIXME: support cross-domain wrappers.
-        if (!instanceOf<BindingsClass>(domData, wrapper)) {
-            String message = String("Invalid class: expected instance of ") + BindingsClass::dartImplementationClassName;
-            exception = DartUtilities::stringToDartString(message);
-            return 0;
+        if (subtypeOf(wrapper, BindingsClass::dartClassId)) {
+            void* nativePointer = readNativePointer(wrapper, kNativeImplementationIndex);
+            return static_cast<typename BindingsClass::NativeType*>(nativePointer);
         }
-        void* nativePointer = readNativePointer(wrapper, kNativeImplementationIndex);
-        return static_cast<typename BindingsClass::NativeType*>(nativePointer);
+        String message = String("Invalid class: expected instance of ") +
+            BindingsClass::dartImplementationClassName;
+        exception = DartUtilities::stringToDartString(message);
+        return 0;
     }
 
     template <class BindingsClass>
@@ -162,6 +164,19 @@
         return unwrapDartWrapper<BindingsClass>(domData, wrapper, exception);
     }
 
+    static bool subtypeOf(Dart_Handle wrapper, intptr_t basecid)
+    {
+        intptr_t cid = reinterpret_cast<intptr_t>(readNativePointer(wrapper, kNativeTypeIndex));
+        while (cid != -1) {
+            if (cid == basecid) {
+                return true;
+            }
+            ASSERT(cid < NumWebkitClassIds);
+            cid = DartWebkitClassInfo[cid].base_class_id;
+        }
+        return false;
+    }
+
     template <class BindingsClass>
     static bool instanceOf(DartDOMData* domData, Dart_Handle wrapper)
     {
@@ -212,6 +227,7 @@
 private:
     enum NativeFieldIndices {
         kNativeImplementationIndex = 0,
+        kNativeTypeIndex = 1,
         kNativeFieldCount
     };
 
@@ -232,12 +248,14 @@
     static Dart_PersistentHandle dartClass(const char* dartImplementationClassName,
         const char* dartImplementationLibraryName, intptr_t classIndex);
 
-    static void writeNativePointer(Dart_Handle wrapper, int index, void* pointer)
+    static void writeNativePointer(Dart_Handle wrapper, void* pointer, intptr_t cid)
     {
         Dart_Handle result = Dart_SetNativeInstanceField(
-            wrapper, index, reinterpret_cast<intptr_t>(pointer));
+            wrapper, kNativeImplementationIndex, reinterpret_cast<intptr_t>(pointer));
         UNUSED_PARAM(result);
         ASSERT(!Dart_IsError(result));
+        result = Dart_SetNativeInstanceField(wrapper, kNativeTypeIndex, cid);
+        ASSERT(!Dart_IsError(result));
     }
 
     static void* readNativePointer(Dart_Handle wrapper, int index)