Track the region where text is painted.

Source/core/platform/graphics/TextRun.h

Index: Source/core/platform/graphics/TextRun.h
diff --git a/Source/core/platform/graphics/TextRun.h b/Source/core/platform/graphics/TextRun.h
index 2d76d2e531c2d1a6568c36e043ed5fa00b828c73..40a5b2a2857a188e3c37f5adb203b3f4a2a42b90 100644
--- a/Source/core/platform/graphics/TextRun.h
+++ b/Source/core/platform/graphics/TextRun.h
@@ -24,6 +24,7 @@
 #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>
@@ -31,7 +32,6 @@
 namespace WebCore {
 
 class FloatPoint;
-class FloatRect;
 class Font;
 class GraphicsContext;
 class GlyphBuffer;
@@ -256,6 +256,20 @@ inline void TextRun::setTabSize(bool allow, unsigned size)
     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