Fix JDWP location event report on return instructions

After change https://android-review.googlesource.com/94334, the debugger may
listen to kDexPcChange event without listening for kMethodExit event. In this
case, we need to report kDexPcChange event on RETURN instructions.

Bug: 11874828
Change-Id: Ic61f4eec71e7ece494bee628d7f3358a616d31d3
diff --git a/runtime/debugger.cc b/runtime/debugger.cc
index edf54be..f6b4891 100644
--- a/runtime/debugger.cc
+++ b/runtime/debugger.cc
@@ -2809,6 +2809,7 @@
     }
     case DeoptimizationRequest::kFullUndeoptimization: {
       DCHECK(req.method == nullptr);
+      DCHECK_GT(full_deoptimization_event_count_, 0U);
       --full_deoptimization_event_count_;
       if (full_deoptimization_event_count_ == 0) {
         VLOG(jdwp) << "Queue request #" << deoptimization_requests_.size()