Support loading vdex files without odex.

GetDexoptNeeded with 'verify' as filter will return false when a vdex is
available.

Test: 628-vdex, 820-vdex-multidex, test.py
Bug: 176960283
Change-Id: I3ac2f747d1e7f5331a49a22c94983959e3b60122
diff --git a/runtime/oat_file_assistant.h b/runtime/oat_file_assistant.h
index 8784875..e771dcc 100644
--- a/runtime/oat_file_assistant.h
+++ b/runtime/oat_file_assistant.h
@@ -430,9 +430,19 @@
   bool required_dex_checksums_found_;
   bool has_original_dex_files_;
 
+  // The AOT-compiled file of an app when the APK of the app is in /data.
   OatFileInfo odex_;
+  // The AOT-compiled file of an app when the APK of the app is on a read-only partition
+  // (for example /system).
   OatFileInfo oat_;
 
+  // The vdex-only file next to `odex_` when `odex_' cannot be used (for example
+  // it is out of date).
+  OatFileInfo vdex_for_odex_;
+  // The vdex-only file next to 'oat_` when `oat_' cannot be used (for example
+  // it is out of date).
+  OatFileInfo vdex_for_oat_;
+
   // File descriptor corresponding to apk, dex file, or zip.
   int zip_fd_;