Use a block cursor in overtype mode

Source/core/editing/FrameSelection.h

Index: Source/core/editing/FrameSelection.h
diff --git a/Source/core/editing/FrameSelection.h b/Source/core/editing/FrameSelection.h
index 119d04c07fb9170f75d60636c9e437b6dfb901c5..9a23674fb60cdb7c8ed7b8c47d81b02459c86029 100644
--- a/Source/core/editing/FrameSelection.h
+++ b/Source/core/editing/FrameSelection.h
@@ -256,6 +256,9 @@ public:
     void revealSelection(const ScrollAlignment& = ScrollAlignment::alignCenterIfNeeded, RevealExtentOption = DoNotRevealExtent);
     void setSelectionFromNone();
 
+    bool shouldShowBlockCursor() const { return m_shouldShowBlockCursor; }
+    void setShouldShowBlockCursor(bool);
+
 private:
     enum EPositionType { START, END, BASE, EXTENT };
 
@@ -312,6 +315,7 @@ private:
     bool m_caretPaint : 1;
     bool m_isCaretBlinkingSuspended : 1;
     bool m_focused : 1;
+    bool m_shouldShowBlockCursor : 1;
 };
 
 inline EditingStyle* FrameSelection::typingStyle() const