[SVGDom] Add <svg> viewBox support

experimental/svg/model/SkSVGSVG.h

Index: experimental/svg/model/SkSVGSVG.h
diff --git a/experimental/svg/model/SkSVGSVG.h b/experimental/svg/model/SkSVGSVG.h
index 27631f5a3169c6c51b35e8eaec6b0688df1a1d60..ae4787cac3cee3f9ef17d2827033e8cfe5efa7c5 100644
--- a/experimental/svg/model/SkSVGSVG.h
+++ b/experimental/svg/model/SkSVGSVG.h
@@ -10,6 +10,7 @@
 
 #include "SkSVGContainer.h"
 #include "SkSVGTypes.h"
+#include "SkTLazy.h"
 
 class SkSVGSVG : public SkSVGContainer {
 public:
@@ -21,8 +22,11 @@ public:
     void setY(const SkSVGLength&);
     void setWidth(const SkSVGLength&);
     void setHeight(const SkSVGLength&);
+    void setViewBox(const SkSVGViewBoxType&);
 
 protected:
+    bool onPrepareToRender(SkSVGRenderContext*) const override;
+
     void onSetAttribute(SkSVGAttribute, const SkSVGValue&) override;
 
 private:
@@ -33,6 +37,8 @@ private:
     SkSVGLength fWidth  = SkSVGLength(100, SkSVGLength::Unit::kPercentage);
     SkSVGLength fHeight = SkSVGLength(100, SkSVGLength::Unit::kPercentage);
 
+    SkTLazy<SkSVGViewBoxType> fViewBox;
+
     typedef SkSVGContainer INHERITED;
 };