ART: Release DexFile in OatFileAssistant

Change-Id: I4ff0041191d2fe7a33c2b55f163a33e92da62b6b
diff --git a/runtime/oat_file_assistant.cc b/runtime/oat_file_assistant.cc
index 6daade0..262c932 100644
--- a/runtime/oat_file_assistant.cc
+++ b/runtime/oat_file_assistant.cc
@@ -468,7 +468,7 @@
       // the DEX code has not been quickened.
       std::string error_msg;
       for (const OatFile::OatDexFile* current : file.GetOatDexFiles()) {
-        const DexFile* const dex_file = current->OpenDexFile(&error_msg).release();
+        std::unique_ptr<const DexFile> dex_file = current->OpenDexFile(&error_msg);
         DCHECK(dex_file != nullptr);
         for (size_t i = 0, e = dex_file->NumClassDefs(); i < e; ++i) {
           DCHECK_EQ(current->GetOatClass(i).GetType(), kOatClassNoneCompiled);