[debugger] simplify debug stepping.

src/isolate.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 2763 matching lines @@
 void Isolate::RemoveCallCompletedCallback(CallCompletedCallback callback) {
   for (int i = 0; i < call_completed_callbacks_.length(); i++) {
     if (callback == call_completed_callbacks_.at(i)) {
       call_completed_callbacks_.Remove(i);
     }
   }
 }
 
 
 void Isolate::FireCallCompletedCallback() {
-  bool has_call_completed_callbacks = !call_completed_callbacks_.is_empty();
+  if (!handle_scope_implementer()->CallDepthIsZero()) return;
+
   bool run_microtasks =
       pending_microtask_count() &&
       !handle_scope_implementer()->HasMicrotasksSuppressions() &&
       handle_scope_implementer()->microtasks_policy() ==
           v8::MicrotasksPolicy::kAuto;
-  if (!has_call_completed_callbacks && !run_microtasks) return;
 
-  if (!handle_scope_implementer()->CallDepthIsZero()) return;
   if (run_microtasks) RunMicrotasks();
+  // Prevent stepping from spilling into the next call made by the embedder.
+  if (debug()->is_active()) debug()->ClearStepping();
+
+  if (call_completed_callbacks_.is_empty()) return;
   // Fire callbacks.  Increase call depth to prevent recursive callbacks.
   v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(this);
   v8::Isolate::SuppressMicrotaskExecutionScope suppress(isolate);
   for (int i = 0; i < call_completed_callbacks_.length(); i++) {
     call_completed_callbacks_.at(i)(isolate);
   }
 }
 
 
 void Isolate::SetPromiseRejectCallback(PromiseRejectCallback callback) {
@@ skipping 259 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8