[SVGDom] Add <svg> viewBox support

experimental/svg/model/SkSVGTypes.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSVGTypes_DEFINED
 #define SkSVGTypes_DEFINED
 
 #include "SkColor.h"
+#include "SkRect.h"
 #include "SkScalar.h"
 #include "SkTypes.h"
 
-class SkSVGNumber {
+template <typename T>
+class SkSVGPrimitiveTypeWrapper {
 public:
-    constexpr SkSVGNumber()                    : fValue(0) {}
-    explicit constexpr SkSVGNumber(SkScalar v) : fValue(v) {}
-    SkSVGNumber(const SkSVGNumber&)            = default;
-    SkSVGNumber& operator=(const SkSVGNumber&) = default;
+    SkSVGPrimitiveTypeWrapper() = default;
+    explicit constexpr SkSVGPrimitiveTypeWrapper(T v) : fValue(v) {}
 
+    SkSVGPrimitiveTypeWrapper(const SkSVGPrimitiveTypeWrapper&)            = default;
+    SkSVGPrimitiveTypeWrapper& operator=(const SkSVGPrimitiveTypeWrapper&) = default;
 
-    const SkScalar& value() const { return fValue; }
-
-    operator const SkScalar&() const { return fValue; }
+    const T& value() const { return fValue; }
+    operator const T&() const { return fValue; }
 
 private:
-    SkScalar fValue;
+    T fValue;
 };
 
+using SkSVGColorType   = SkSVGPrimitiveTypeWrapper<SkColor >;
+using SkSVGNumberType  = SkSVGPrimitiveTypeWrapper<SkScalar>;
+using SkSVGViewBoxType = SkSVGPrimitiveTypeWrapper<SkRect  >;
+
 class SkSVGLength {
 public:
     enum class Unit {
         kUnknown,
         kNumber,
         kPercentage,
         kEMS,
         kEXS,
         kPX,
         kCM,
@@ skipping 10 matching lines @@
     SkSVGLength& operator=(const SkSVGLength&) = default;
 
     const SkScalar& value() const { return fValue; }
     const Unit&     unit()  const { return fUnit;  }
 
 private:
     SkScalar fValue;
     Unit     fUnit;
 };
 
-class SkSVGColor {
-public:
-    constexpr SkSVGColor()                   : fValue(SK_ColorBLACK) {}
-    explicit constexpr SkSVGColor(SkColor c) : fValue(c) {}
-
-    operator const SkColor&() const { return fValue; }
-
-private:
-    SkColor fValue;
-};
-
 #endif // SkSVGTypes_DEFINED