Use Java strings for Field's name.

Change-Id: Ia75c9c0ed0a802e52e415d856a101affb9fddd8a
diff --git a/src/object.h b/src/object.h
index a9bf40f..0f89411 100644
--- a/src/object.h
+++ b/src/object.h
@@ -257,8 +257,8 @@
     return declaring_class_;
   }
 
-  const StringPiece& GetName() const {
-    return name_;
+  const String* GetName() const {
+    return java_name_;
   }
 
   char GetType() const {  // TODO: return type
@@ -986,6 +986,7 @@
 std::ostream& operator<<(std::ostream& os, const Class::Status& rhs);
 
 inline Object* Object::Alloc(Class* klass) {
+  DCHECK(klass != NULL);
   return Heap::AllocObject(klass, klass->object_size_);
 }