Release execution lock before dispatching interrupt handling.

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index 8b33087e046b70a66630d0773756571c90a21390..150664988969beae18d249a69b80889aff40a2c9 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -2571,6 +2571,8 @@ MaybeHandle<Object> Debug::MakeJSObject(
       isolate_->global_object(), constructor_str).ToHandleChecked();
   ASSERT(constructor->IsJSFunction());
   if (!constructor->IsJSFunction()) return MaybeHandle<Object>();
+  // We do not handle interrupts here.  In particular, termination interrupts.
+  PostponeInterruptsScope no_interrupts(isolate_);
   return Execution::TryCall(
       Handle<JSFunction>::cast(constructor),
       Handle<JSObject>(isolate_->debug()->debug_context()->global_object()),
@@ -2907,6 +2909,9 @@ void Debug::NotifyMessageHandler(v8::DebugEvent event,
                                  Handle<JSObject> exec_state,
                                  Handle<JSObject> event_data,
                                  bool auto_continue) {
+  // Prevent other interrupts from triggering, for example API callbacks,
+  // while dispatching message handler callbacks.
+  PostponeInterruptsScope no_interrupts(isolate_);
   ASSERT(is_active_);
   HandleScope scope(isolate_);
   // Process the individual events.