Fix call stack sampling for the case when native callback invokes JS function

src/vm-state.h

Index: src/vm-state.h
diff --git a/src/vm-state.h b/src/vm-state.h
index 765b5701595b7f9637da05b0783662d603506463..f592bb92ca5f4338ebf44853b256a84dca0ffc54 100644
--- a/src/vm-state.h
+++ b/src/vm-state.h
@@ -50,9 +50,18 @@ class ExternalCallbackScope BASE_EMBEDDED {
  public:
   inline ExternalCallbackScope(Isolate* isolate, Address callback);
   inline ~ExternalCallbackScope();
+  Address callback() { return callback_; }
+  Address* callback_address() { return &callback_; }
+  ExternalCallbackScope* previous() { return previous_scope_; }
+  inline Address scope_address();
+
  private:
   Isolate* isolate_;
-  Address previous_callback_;
+  Address callback_;
+  ExternalCallbackScope* previous_scope_;
+#ifdef USE_SIMULATOR
+  Address scope_address_;
+#endif
 };
 
 } }  // namespace v8::internal