ART: Add dex::StringIndex

Add abstraction for uint32_t string index.

Test: m test-art-host
Change-Id: I917c2881702fe3df112c713f06980f2278ced7ed
diff --git a/runtime/entrypoints/quick/quick_dexcache_entrypoints.cc b/runtime/entrypoints/quick/quick_dexcache_entrypoints.cc
index b1259e1..5dad43e 100644
--- a/runtime/entrypoints/quick/quick_dexcache_entrypoints.cc
+++ b/runtime/entrypoints/quick/quick_dexcache_entrypoints.cc
@@ -66,7 +66,7 @@
       // TODO: Change art_quick_resolve_string on MIPS and MIPS64 to kSaveEverything.
       (kRuntimeISA == kMips || kRuntimeISA == kMips64) ? Runtime::kSaveRefsOnly
                                                        : Runtime::kSaveEverything);
-  mirror::String* result = ResolveStringFromCode(caller, string_idx);
+  mirror::String* result = ResolveStringFromCode(caller, dex::StringIndex(string_idx));
   if (LIKELY(result != nullptr)) {
     // For AOT code, we need a write barrier for the class loader that holds
     // the GC roots in the .bss.