Keep a cache of caret painters to avoid recomputing all the time.

Source/core/paint/BlockPainter.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BlockPainter_h
 #define BlockPainter_h
 
 namespace blink {
 
 struct PaintInfo;
 class InlineBox;
 class LayoutBlock;
 class LayoutBox;
 class LayoutFlexibleBox;
 class LayoutObject;
 class LayoutPoint;
 class LayoutRect;
+class LocalFrame;
+class PaintDataCache;
 
 class BlockPainter {
 public:
     BlockPainter(LayoutBlock& block) : m_layoutBlock(block) { }
 
     void paint(const PaintInfo&, const LayoutPoint& paintOffset);
     void paintObject(const PaintInfo&, const LayoutPoint&);
     void paintChildren(const PaintInfo&, const LayoutPoint&);
     void paintChild(LayoutBox&, const PaintInfo&, const LayoutPoint&);
     void paintChildAsInlineBlock(LayoutBox&, const PaintInfo&, const LayoutPoint&);
     void paintOverflowControlsIfNeeded(const PaintInfo&, const LayoutPoint&);
 
     // inline-block elements paint all phases atomically. This function ensures that. Certain other elements
     // (grid items, flex items) require this behavior as well, and this function exists as a helper for them.
     // It is expected that the caller will call this function independent of the value of paintInfo.phase.
     static void paintAsInlineBlock(LayoutObject&, const PaintInfo&, const LayoutPoint&);
     static void paintChildrenOfFlexibleBox(LayoutFlexibleBox&, const PaintInfo&, const LayoutPoint& paintOffset);
     static void paintInlineBox(InlineBox&, const PaintInfo&, const LayoutPoint& paintOffset);
 
 private:
     LayoutRect overflowRectForPaintRejection() const;
-    bool hasCaret() const;
+    bool hasCaret(PaintDataCache* = nullptr) const;
     void paintCarets(const PaintInfo&, const LayoutPoint&);
     void paintContents(const PaintInfo&, const LayoutPoint&);
     void paintSelection(const PaintInfo&, const LayoutPoint&);
     void paintContinuationOutlines(const PaintInfo&, const LayoutPoint&);
 
     LayoutBlock& m_layoutBlock;
 };
 
 } // namespace blink
 
 #endif // BlockPainter_h