Add a "vdex" reason for compilation reason.

When the oat file is out of date, we run directly from the vdex.

Test: test.py
Bug: 192408935
Change-Id: I7474532d7f12a32d2c26a5a0fb8b73671793d3f3
diff --git a/libartbase/base/metrics/metrics.h b/libartbase/base/metrics/metrics.h
index 17fb0d8..d6f2463 100644
--- a/libartbase/base/metrics/metrics.h
+++ b/libartbase/base/metrics/metrics.h
@@ -100,7 +100,8 @@
   V(kShared, "shared") \
   V(kInstallWithDexMetadata, "install-with-dex-metadata") \
   V(kPrebuilt, "prebuilt") \
-  V(kCmdLine, "cmdline")
+  V(kCmdLine, "cmdline") \
+  V(kVdex, "vdex")
 
 // We log compilation reasons as part of the metadata we report. Since elsewhere compilation reasons
 // are specified as a string, we define them as an enum here which indicates the reasons that we