[inspector] V8DebuggerAgent cleanup

src/debug/debug.cc

Index: src/debug/debug.cc
diff --git a/src/debug/debug.cc b/src/debug/debug.cc
index b732303fc8572bec2abf1c89edc8c7924b77743c..fe915f6c4321719334a6646765e7b1403520dd42 100644
--- a/src/debug/debug.cc
+++ b/src/debug/debug.cc
@@ -1000,6 +1000,17 @@ void Debug::PrepareStep(StepAction step_action) {
 
   BreakLocation location = BreakLocation::FromFrame(debug_info, js_frame);
 
+  // It is used at least in two cases:
+  // - step-next at return position from first callback in microtask will break
+  // in next callback,
+  // - step-next at return position when caller frame is blackboxed will break
+  // in next not blackboxed function called by caller frame if any.
+  // TODO(kozyatinskiy): remove it.
+  if (step_action == StepNext && location.IsReturn()) {
+    thread_local_.last_step_action_ = StepIn;
+    UpdateHookOnFunctionCall();
+  }
+
   // Any step at a return is a step-out.
   if (location.IsReturn()) step_action = StepOut;
   // A step-next at a tail call is a step-out.
@@ -1766,9 +1777,10 @@ void Debug::OnException(Handle<Object> exception, Handle<Object> promise) {
 
   {
     JavaScriptFrameIterator it(isolate_);
-    // Check whether the top frame is blackboxed or the break location is muted.
-    if (!it.done() && (IsMutedAtCurrentLocation(it.frame()) ||
-                       IsExceptionBlackboxed(uncaught))) {
+    // Check whether the top frame is blackboxed or the break location is muted
+    // or current JS stack trace is empty.
+    if (it.done() || IsMutedAtCurrentLocation(it.frame()) ||
+        IsExceptionBlackboxed(uncaught)) {
       return;
     }
   }