Use VM type cast and save handles.

runtime/vm/object.h

Index: runtime/vm/object.h
===================================================================
--- runtime/vm/object.h	(revision 9315)
+++ runtime/vm/object.h	(working copy)
@@ -92,6 +92,9 @@
   static object& CheckedZoneHandle(RawObject* raw_ptr) {                       \
     return CheckedZoneHandle(Isolate::Current(), raw_ptr);                     \
   }                                                                            \
+  /* T::Cast cannot be applied to a null Object, because the object vtable */  \
+  /* is not setup for type T, although some methods are supposed to work   */  \
+  /* with null, for example Instance::Equals().                            */  \
   static const object& Cast(const Object& obj) {                               \
     ASSERT(obj.Is##object());                                                  \
     return reinterpret_cast<const object&>(obj);                               \
@@ -5074,12 +5077,9 @@
 Token::Kind TokenStream::KindAt(intptr_t index) const {
   const Object& obj = Object::Handle(TokenAt(index));
   if (obj.IsSmi()) {
-    return static_cast<Token::Kind>(
-        Smi::Value(reinterpret_cast<RawSmi*>(obj.raw())));
+    return static_cast<Token::Kind>(Smi::Cast(obj).Value());
   } else if (obj.IsLiteralToken()) {
-    LiteralToken& token = LiteralToken::Handle();
-    token ^= obj.raw();
-    return token.kind();
+    return LiteralToken::Cast(obj).kind();
   }
   ASSERT(obj.IsString());  // Must be an identifier.
   return Token::kIDENT;