Avoid handle-less fields in ClassLinker::InitializeClass()

There were some handle-less fields in a SafeMap across GC points.

Bug: 12687968
Change-Id: Ib8c6527d4e23031f1d0074fa11d8f85499b68340
diff --git a/runtime/dex_file.h b/runtime/dex_file.h
index 2794af6..1e86bfc 100644
--- a/runtime/dex_file.h
+++ b/runtime/dex_file.h
@@ -1199,7 +1199,7 @@
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   template<bool kTransactionActive>
-  void ReadValueToField(mirror::ArtField* field) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  void ReadValueToField(Handle<mirror::ArtField> field) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   bool HasNext() { return pos_ < array_size_; }