ART: Add Agent Thread API

Add support for RunAgentThread. Add test.

Bug: 31684593
Test: m test-art-host-run-test-931-agent-thread
Change-Id: I5deb213fb06eedc5ee78a340458cf0dff615d0ac
diff --git a/test/Android.bp b/test/Android.bp
index 965d07a..be5bc59 100644
--- a/test/Android.bp
+++ b/test/Android.bp
@@ -269,6 +269,7 @@
         "927-timers/timers.cc",
         "928-jni-table/jni_table.cc",
         "929-search/search.cc",
+        "931-agent-thread/agent_thread.cc",
     ],
     shared_libs: [
         "libbase",