Reland of place all remaining Oddball checks with new function

src/api.h

Index: src/api.h
diff --git a/src/api.h b/src/api.h
index cb2b5c386c2cce09c6ce062cbcc181b3c98a32d8..a6f403d75d2f1a154d8d40a0b9aef686792bce61 100644
--- a/src/api.h
+++ b/src/api.h
@@ -281,7 +281,9 @@
 
   template<class From, class To>
   static inline Local<To> Convert(v8::internal::Handle<From> obj) {
-    DCHECK(obj.is_null() || !obj->IsTheHole());
+    DCHECK(obj.is_null() ||
+           (obj->IsSmi() ||
+            !obj->IsTheHole(i::HeapObject::cast(*obj)->GetIsolate())));
     return Local<To>(reinterpret_cast<To*>(obj.location()));
   }