For JDWP, suspend thread before configuring it for single stepping.

Change-Id: I05a7c28c9e977885195797a78a492aa0f72801b7
diff --git a/src/jdwp/jdwp_event.cc b/src/jdwp/jdwp_event.cc
index 5b65aa4..56ba131 100644
--- a/src/jdwp/jdwp_event.cc
+++ b/src/jdwp/jdwp_event.cc
@@ -143,8 +143,6 @@
  * not be added to the list, and an appropriate error will be returned.
  */
 JdwpError JdwpState::RegisterEvent(JdwpEvent* pEvent) {
-  MutexLock mu(Thread::Current(), event_list_lock_);
-
   CHECK(pEvent != NULL);
   CHECK(pEvent->prev == NULL);
   CHECK(pEvent->next == NULL);
@@ -175,6 +173,7 @@
   /*
    * Add to list.
    */
+  MutexLock mu(Thread::Current(), event_list_lock_);
   if (event_list_ != NULL) {
     pEvent->next = event_list_;
     event_list_->prev = pEvent;