Use Length for the stroke-dashoffset property in SVGLayoutStyle

Source/core/layout/style/LayoutStyle.h

Index: Source/core/layout/style/LayoutStyle.h
diff --git a/Source/core/layout/style/LayoutStyle.h b/Source/core/layout/style/LayoutStyle.h
index b4024790999a2359b10a46cf7cf0b6a0b224c9f7..5b802afd3b8ea87e9c85e4cbb890c8ab68ba4179 100644
--- a/Source/core/layout/style/LayoutStyle.h
+++ b/Source/core/layout/style/LayoutStyle.h
@@ -1367,8 +1367,8 @@ public:
     void setStrokeWidth(PassRefPtrWillBeRawPtr<SVGLength> w) { accessSVGStyle().setStrokeWidth(w); }
     SVGLengthList* strokeDashArray() const { return svgStyle().strokeDashArray(); }
     void setStrokeDashArray(PassRefPtrWillBeRawPtr<SVGLengthList> array) { accessSVGStyle().setStrokeDashArray(array); }
-    SVGLength* strokeDashOffset() const { return svgStyle().strokeDashOffset(); }
-    void setStrokeDashOffset(PassRefPtrWillBeRawPtr<SVGLength> d) { accessSVGStyle().setStrokeDashOffset(d); }
+    const Length& strokeDashOffset() const { return svgStyle().strokeDashOffset(); }
+    void setStrokeDashOffset(const Length& d) { accessSVGStyle().setStrokeDashOffset(d); }
     float strokeMiterLimit() const { return svgStyle().strokeMiterLimit(); }
     void setStrokeMiterLimit(float f) { accessSVGStyle().setStrokeMiterLimit(f); }