[svg2] Make 'x' and 'y' presentation attributes

Source/core/svg/SVGLengthContext.h

Index: Source/core/svg/SVGLengthContext.h
diff --git a/Source/core/svg/SVGLengthContext.h b/Source/core/svg/SVGLengthContext.h
index 758cb6d93988def38c597b93d4bed46187517be3..2dfb3d1bdc9c550bcc32b438682d237571648e59 100644
--- a/Source/core/svg/SVGLengthContext.h
+++ b/Source/core/svg/SVGLengthContext.h
@@ -21,6 +21,7 @@
 #define SVGLengthContext_h
 
 #include "core/svg/SVGUnitTypes.h"
+#include "platform/Length.h"
 #include "platform/geometry/FloatRect.h"
 
 namespace blink {
@@ -64,6 +65,8 @@ public:
     static FloatPoint resolvePoint(const SVGElement*, SVGUnitTypes::SVGUnitType, PassRefPtrWillBeRawPtr<SVGLength> x, PassRefPtrWillBeRawPtr<SVGLength> y);
     static float resolveLength(const SVGElement*, SVGUnitTypes::SVGUnitType, PassRefPtrWillBeRawPtr<SVGLength>);
 
+    float valueForLength(const Length&, SVGLengthMode = LengthModeOther);
+
     float convertValueToUserUnits(float, SVGLengthMode, SVGLengthType fromUnit, ExceptionState&) const;

[fs, 2015/02/06 12:28:53]

If https://codereview.chromium.org/901193002/ lands before this, it's possible
you get a conflict here and in the .cpp file. Should be a trivial modify-add
thing though.

     float convertValueFromUserUnits(float, SVGLengthMode, SVGLengthType toUnit, ExceptionState&) const;