ART: Add ThreadStart & ThreadEnd

Add support for ThreadStart and ThreadEnd events. Add tests.

Bug: 31684920
Test: m test-art-host-run-test-924-threads
Change-Id: I516993402747ffdc9a7d66985b21b95c059be107
diff --git a/runtime/openjdkjvmti/ti_thread.h b/runtime/openjdkjvmti/ti_thread.h
index 5aaec58..f6f93ee 100644
--- a/runtime/openjdkjvmti/ti_thread.h
+++ b/runtime/openjdkjvmti/ti_thread.h
@@ -37,8 +37,13 @@
 
 namespace openjdkjvmti {
 
+class EventHandler;
+
 class ThreadUtil {
  public:
+  static void Register(EventHandler* event_handler);
+  static void Unregister();
+
   static jvmtiError GetAllThreads(jvmtiEnv* env, jint* threads_count_ptr, jthread** threads_ptr);
 
   static jvmtiError GetCurrentThread(jvmtiEnv* env, jthread* thread_ptr);