[SVG2] Add support for the 'turn' unit in <angle>.

Source/core/svg/SVGAngleTearOff.h

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 36 matching lines @@
     enum {
         SVG_ANGLETYPE_UNKNOWN = SVGAngle::SVG_ANGLETYPE_UNKNOWN,
         SVG_ANGLETYPE_UNSPECIFIED = SVGAngle::SVG_ANGLETYPE_UNSPECIFIED,
         SVG_ANGLETYPE_DEG = SVGAngle::SVG_ANGLETYPE_DEG,
         SVG_ANGLETYPE_RAD = SVGAngle::SVG_ANGLETYPE_RAD,
         SVG_ANGLETYPE_GRAD = SVGAngle::SVG_ANGLETYPE_GRAD
     };
 
     virtual ~SVGAngleTearOff();
 
-    unsigned short unitType() { return target()->unitType(); }
+    unsigned short unitType() { return hasExposedAngleUnit() ? target()->unitType() : SVGAngle::SVG_ANGLETYPE_UNKNOWN; }
 
     void setValue(float, ExceptionState&);
     float value() { return target()->value(); }
 
     void setValueInSpecifiedUnits(float, ExceptionState&);
     float valueInSpecifiedUnits() { return target()->valueInSpecifiedUnits(); }
 
     void newValueSpecifiedUnits(unsigned short unitType, float valueInSpecifiedUnits, ExceptionState&);
     void convertToSpecifiedUnits(unsigned short unitType, ExceptionState&);
 
-    String valueAsString() { return target()->valueAsString(); }
+    String valueAsString() { return hasExposedAngleUnit() ? target()->valueAsString() : String::number(0); }
     void setValueAsString(const String&, ExceptionState&);
 
 private:
     SVGAngleTearOff(PassRefPtr<SVGAngle>, SVGElement*, PropertyIsAnimValType, const QualifiedName&);
+
+    bool hasExposedAngleUnit() { return target()->unitType() <= SVGAngle::SVG_ANGLETYPE_GRAD; }
 };
 
 } // namespace WebCore
 
 #endif // SVGAngleTearOff_h_