[SVGDom] Add <svg> viewBox support

experimental/svg/model/SkSVGTransformableNode.cpp

Index: experimental/svg/model/SkSVGTransformableNode.cpp
diff --git a/experimental/svg/model/SkSVGTransformableNode.cpp b/experimental/svg/model/SkSVGTransformableNode.cpp
index 3636754fcc80c5c18affd8895e80a2773e2f86c5..2686a4c5423d681ede38c94013b2aa21fcf488eb 100644
--- a/experimental/svg/model/SkSVGTransformableNode.cpp
+++ b/experimental/svg/model/SkSVGTransformableNode.cpp
@@ -5,6 +5,8 @@
  * found in the LICENSE file.
  */
 
+#include "SkCanvas.h"
+#include "SkSVGRenderContext.h"
 #include "SkSVGTransformableNode.h"
 #include "SkSVGValue.h"
 
@@ -12,6 +14,16 @@ SkSVGTransformableNode::SkSVGTransformableNode(SkSVGTag tag)
     : INHERITED(tag)
     , fMatrix(SkMatrix::I()) { }
 
+
+bool SkSVGTransformableNode::onPrepareToRender(SkSVGRenderContext* ctx) const {
+    if (!fMatrix.isIdentity()) {
+        ctx->canvas()->save();
+        ctx->canvas()->concat(fMatrix);
+    }
+
+    return this->INHERITED::onPrepareToRender(ctx);
+}
+
 void SkSVGTransformableNode::onSetAttribute(SkSVGAttribute attr, const SkSVGValue& v) {
     switch (attr) {
     case SkSVGAttribute::kTransform: