ART: Add dex::StringIndex

Add abstraction for uint32_t string index.

Test: m test-art-host
Change-Id: I917c2881702fe3df112c713f06980f2278ced7ed
diff --git a/runtime/art_field.h b/runtime/art_field.h
index cacb324..427e103 100644
--- a/runtime/art_field.h
+++ b/runtime/art_field.h
@@ -221,7 +221,7 @@
       REQUIRES_SHARED(Locks::mutator_lock_);
   ObjPtr<mirror::String> ResolveGetStringName(Thread* self,
                                               const DexFile& dex_file,
-                                              uint32_t string_idx,
+                                              dex::StringIndex string_idx,
                                               ObjPtr<mirror::DexCache> dex_cache)
       REQUIRES_SHARED(Locks::mutator_lock_);