Support 'paint-order' from SVG2.

Source/core/rendering/style/SVGRenderStyle.cpp

Index: Source/core/rendering/style/SVGRenderStyle.cpp
diff --git a/Source/core/rendering/style/SVGRenderStyle.cpp b/Source/core/rendering/style/SVGRenderStyle.cpp
index 6e796fd9ab0fa73ce1f71c962e6d07ff882f40fc..6d7805446d0b712cff449ba2d344cf3205fd9a4f 100644
--- a/Source/core/rendering/style/SVGRenderStyle.cpp
+++ b/Source/core/rendering/style/SVGRenderStyle.cpp
@@ -227,4 +227,11 @@ StyleDifference SVGRenderStyle::diff(const SVGRenderStyle* other) const
     return StyleDifferenceEqual;
 }
 
+EPaintOrderType SVGRenderStyle::paintOrderType(unsigned index) const
+{
+    ASSERT(index < 3);

[pdr., 2013/06/25 15:30:45]

Can you turn this 3 into a constant? I worry that we'll forget what it's for in
a years time.

+    unsigned pt = (paintOrder() >> (kPaintOrderBitwidth*index)) & ((1u << kPaintOrderBitwidth) - 1);
+    return (EPaintOrderType)pt;
+}
+
 }