Track the region where text is painted.

Source/core/platform/graphics/TextRun.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2011 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef TextRun_h
 #define TextRun_h
 
+#include "core/platform/graphics/FloatRect.h"
 #include "core/platform/text/TextDirection.h"
 #include <wtf/RefCounted.h>
 #include <wtf/text/WTFString.h>
 
 namespace WebCore {
 
 class FloatPoint;
-class FloatRect;
 class Font;
 class GraphicsContext;
 class GlyphBuffer;
 class SimpleFontData;
 struct GlyphData;
 struct WidthIterator;
 
 class TextRun {
     WTF_MAKE_FAST_ALLOCATED;
 public:
@@ skipping 204 matching lines @@
     unsigned m_tabSize;
     RefPtr<RenderingContext> m_renderingContext;
 };
 
 inline void TextRun::setTabSize(bool allow, unsigned size)
 {
     m_allowTabs = allow;
     m_tabSize = size;
 }
 
+// Container for parameters needed to paint TextRun.
+struct TextRunPaintInfo {
+    explicit TextRunPaintInfo(const TextRun& r)
+        : run(r)
+        , from(0)
+        , to(r.length())
+    {
+    }
+
+    const TextRun& run;
+    int from;
+    int to;
+    FloatRect bounds;
+};
+
 }
-
 #endif