[Experiment] DCHECK clean layout tree in mostForward/BackwardCaretPosition

third_party/WebKit/Source/core/editing/FrameSelection.h

Index: third_party/WebKit/Source/core/editing/FrameSelection.h
diff --git a/third_party/WebKit/Source/core/editing/FrameSelection.h b/third_party/WebKit/Source/core/editing/FrameSelection.h
index 4b609af678dfd4e2a3ec142aa91b85a698d9bfc8..0f5dc20f26a54f7c0991f7d6aa62c7feb18ef08e 100644
--- a/third_party/WebKit/Source/core/editing/FrameSelection.h
+++ b/third_party/WebKit/Source/core/editing/FrameSelection.h
@@ -277,6 +277,8 @@ class CORE_EXPORT FrameSelection final
   // to use updated selection, we should make |updateIfNeeded()| private.
   void updateIfNeeded();
 
+  bool inUpdateSelectionIfNeeded() const { return m_inUpdateSelectionIfNeeded; }
+
   DECLARE_TRACE();
 
  private:
@@ -341,6 +343,8 @@ class CORE_EXPORT FrameSelection final
 
   const Member<FrameCaret> m_frameCaret;
   bool m_useSecureKeyboardEntryWhenActive = false;
+
+  bool m_inUpdateSelectionIfNeeded = false;
 };
 
 inline EditingStyle* FrameSelection::typingStyle() const {