ART: Add dex::TypeIndex

Add abstraction for uint16_t type index.

Test: m test-art-host
Change-Id: I47708741c7c579cbbe59ab723c1e31c5fe71f83a
diff --git a/runtime/arch/stub_test.cc b/runtime/arch/stub_test.cc
index bbf9a8b..6665897 100644
--- a/runtime/arch/stub_test.cc
+++ b/runtime/arch/stub_test.cc
@@ -1063,7 +1063,7 @@
   EXPECT_FALSE(self->IsExceptionPending());
   {
     // Use an arbitrary method from c to use as referrer
-    size_t result = Invoke3(static_cast<size_t>(c->GetDexTypeIndex()),    // type_idx
+    size_t result = Invoke3(static_cast<size_t>(c->GetDexTypeIndex().index_),    // type_idx
                             // arbitrary
                             reinterpret_cast<size_t>(c->GetVirtualMethod(0, kRuntimePointerSize)),
                             0U,
@@ -1197,7 +1197,7 @@
   if ((false)) {
     // Use an arbitrary method from c to use as referrer
     size_t result = Invoke3(
-        static_cast<size_t>(c->GetDexTypeIndex()),    // type_idx
+        static_cast<size_t>(c->GetDexTypeIndex().index_),    // type_idx
         10U,
         // arbitrary
         reinterpret_cast<size_t>(c_obj->GetVirtualMethod(0, kRuntimePointerSize)),