Optimize glyph positioning for SVG <textPath> layout

Source/core/rendering/svg/SVGTextLayoutEngine.h

Index: Source/core/rendering/svg/SVGTextLayoutEngine.h
diff --git a/Source/core/rendering/svg/SVGTextLayoutEngine.h b/Source/core/rendering/svg/SVGTextLayoutEngine.h
index 3ae5fa09087e13905509ae4a98199fb50e886988..b0fd0ca8b44c56bb971a2a1f78370fa3a08e41ee 100644
--- a/Source/core/rendering/svg/SVGTextLayoutEngine.h
+++ b/Source/core/rendering/svg/SVGTextLayoutEngine.h
@@ -96,7 +96,7 @@ private:
     bool m_inPathLayout;
 
     // Text on path layout
-    Path m_textPath;
+    OwnPtr<Path::PositionCalculator> m_textPathCalculator;

[Stephen Chennney, 2014/02/07 16:16:05]

The lifetime of this appears to be within the
beginTextPathLayout/endTextPathLayout, whereas OwnPtr implies something that
should be automatically deleted on destruction of the owner. I presume that the
SVGTextLayoutEngine will not be destructed within the begin/end. So this should
be a raw pointer.

[fs, 2014/02/07 17:09:19]

Right. Changed.

     float m_textPathLength;
     float m_textPathStartOffset;
     float m_textPathCurrentOffset;