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

Source/core/paint/PaintDataCache.cpp

Index: Source/core/paint/PaintDataCache.cpp
diff --git a/Source/core/paint/PaintDataCache.cpp b/Source/core/paint/PaintDataCache.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f074b2e2b6da941eaaafbadeb8863e1ca9e3f6e4
--- /dev/null
+++ b/Source/core/paint/PaintDataCache.cpp
@@ -0,0 +1,32 @@
+// Copyright 2015 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.
+
+#include "config.h"
+#include "core/paint/PaintDataCache.h"
+
+#include "core/editing/Caret.h"
+#include "core/editing/FrameSelection.h"
+#include "core/frame/LocalFrame.h"
+#include "core/frame/Settings.h"
+#include "core/page/Page.h"
+
+namespace blink {
+
+void PaintDataCache::updateCaretCacheForFrame(const LocalFrame* frame)
+{
+    m_caretFrame = frame;
+
+    Settings* settings = frame->settings();
+    bool caretBrowsing = settings && settings->caretBrowsingEnabled();
+
+    const FrameSelection& selection = frame->selection();
+    m_cursorCaretLayoutObject = (selection.hasEditableStyle() || caretBrowsing)
+        ? selection.caretLayoutObject() : nullptr;
+
+    const DragCaretController& dragCaretController = frame->page()->dragCaretController();
+    m_dragCaretLayoutObject = (dragCaretController.isContentEditable() || caretBrowsing)
+        ? dragCaretController.caretLayoutObject() : nullptr;
+}
+
+} // namespace blink