Use VM type cast and save handles.

runtime/vm/native_entry.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_NATIVE_ENTRY_H_
 #define VM_NATIVE_ENTRY_H_
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
 #include "vm/exceptions.h"
@@ skipping 38 matching lines @@
   }                                                                            \
   static void DN_Helper##name(Isolate* isolate, NativeArguments* arguments)
 
 
 #define DECLARE_NATIVE_ENTRY(name, argument_count)                             \
   extern void NATIVE_ENTRY_FUNCTION(name)(Dart_NativeArguments arguments);
 
 // Natives should throw an exception if an illegal argument is passed.
 // type name = value.
 #define GET_NATIVE_ARGUMENT(type, name, value)                                 \
-  type& name = type::Handle();                                                 \
-  {                                                                            \
-    const Instance& __instance__ = Instance::CheckedHandle(value);             \
-    if (!__instance__.Is##type()) {                                            \
-      GrowableArray<const Object*> __args__;                                   \
-      __args__.Add(&__instance__);                                             \
-      Exceptions::ThrowByType(Exceptions::kIllegalArgument, __args__);         \
-    }                                                                          \
-    name ^= __instance__.raw();                                                \
-  }
+  const Instance& __##name##_instance__ = Instance::CheckedHandle(value);      \
+  if (!__##name##_instance__.Is##type()) {                                     \
+    GrowableArray<const Object*> __args__;                                     \
+    __args__.Add(&__##name##_instance__);                                      \
+    Exceptions::ThrowByType(Exceptions::kIllegalArgument, __args__);           \
+  }                                                                            \
+  const type& name = type::Cast(__##name##_instance__);
 
 
 
 // Helper class for resolving and handling native functions.
 class NativeEntry : public AllStatic {
  public:
   // Resolve specified dart native function to the actual native entrypoint.
   static NativeFunction ResolveNative(const Class& cls,
                                       const String& function_name,
                                       int number_of_arguments);
 };
 
 }  // namespace dart
 
 #endif  // VM_NATIVE_ENTRY_H_