Add CaretBase::m_caretPainter, and compute caretBrowsing lazily.

Source/core/editing/Caret.h

Index: Source/core/editing/Caret.h
diff --git a/Source/core/editing/Caret.h b/Source/core/editing/Caret.h
index b411e3f411555e53718ac706c43eac063f1b3c8b..4331e54b6b613db145f7e9c449ee19db9bf73e02 100644
--- a/Source/core/editing/Caret.h
+++ b/Source/core/editing/Caret.h
@@ -59,16 +59,17 @@ protected:
     void paintCaret(Node*, GraphicsContext*, const LayoutPoint&, const LayoutRect& clipRect) const;
 
     const LayoutRect& localCaretRectWithoutUpdate() const { return m_caretLocalRect; }
+    LayoutBlock* caretPainter() const { return m_caretPainter; }
 
     void setCaretVisibility(CaretVisibility visibility) { m_caretVisibility = visibility; }
     bool caretIsVisible() const { return m_caretVisibility == Visible; }
     CaretVisibility caretVisibility() const { return m_caretVisibility; }
 
-protected:
     static LayoutBlock* caretLayoutObject(Node*);
     static void invalidateLocalCaretRect(Node*, const LayoutRect&);
 
 private:
+    LayoutBlock* m_caretPainter; // layout object responsible for painting the caret
     LayoutRect m_caretLocalRect; // caret rect in coords local to the layoutObject responsible for painting the caret
     CaretVisibility m_caretVisibility;
 };
@@ -79,7 +80,7 @@ class DragCaretController final : public NoBaseWillBeGarbageCollected<DragCaretC
 public:
     static PassOwnPtrWillBeRawPtr<DragCaretController> create();
 
-    LayoutBlock* caretLayoutObject() const;
+    LayoutBlock* caretLayoutObject() const { return CaretBase::caretPainter(); }
     void paintDragCaret(LocalFrame*, GraphicsContext*, const LayoutPoint&, const LayoutRect& clipRect) const;
 
     bool isContentEditable() const { return m_position.rootEditableElement(); }