ART: Add dex::TypeIndex

Add abstraction for uint16_t type index.

Test: m test-art-host
Change-Id: I47708741c7c579cbbe59ab723c1e31c5fe71f83a
diff --git a/runtime/dex_file-inl.h b/runtime/dex_file-inl.h
index 621b2c5..77a63c1 100644
--- a/runtime/dex_file-inl.h
+++ b/runtime/dex_file-inl.h
@@ -58,12 +58,12 @@
   return StringDataAndUtf16LengthByIdx(idx, &unicode_length);
 }
 
-inline const char* DexFile::StringByTypeIdx(uint32_t idx, uint32_t* unicode_length) const {
+inline const char* DexFile::StringByTypeIdx(dex::TypeIndex idx, uint32_t* unicode_length) const {
   const TypeId& type_id = GetTypeId(idx);
   return StringDataAndUtf16LengthByIdx(type_id.descriptor_idx_, unicode_length);
 }
 
-inline const char* DexFile::StringByTypeIdx(uint32_t idx) const {
+inline const char* DexFile::StringByTypeIdx(dex::TypeIndex idx) const {
   const TypeId& type_id = GetTypeId(idx);
   return StringDataByIdx(type_id.descriptor_idx_);
 }