[SVGDom] Initial linear gradient support

experimental/svg/model/SkSVGLinearGradient.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 SkSVGLinearGradient_DEFINED
+#define SkSVGLinearGradient_DEFINED
+
+#include "SkSVGHiddenContainer.h"
+#include "SkSVGTypes.h"
+
+class SkSVGLinearGradient : public SkSVGHiddenContainer {
+public:
+    virtual ~SkSVGLinearGradient() = default;
+    static sk_sp<SkSVGLinearGradient> Make() {
+        return sk_sp<SkSVGLinearGradient>(new SkSVGLinearGradient());
+    }
+
+    void setHref(const SkSVGStringType&);
+    void setX1(const SkSVGLength&);
+    void setY1(const SkSVGLength&);
+    void setX2(const SkSVGLength&);
+    void setY2(const SkSVGLength&);
+
+protected:
+    bool onAsPaint(const SkSVGRenderContext&, SkPaint*) const override;
+
+    void onSetAttribute(SkSVGAttribute, const SkSVGValue&) override;
+
+private:
+    SkSVGLinearGradient();
+
+    void collectColorStops(const SkSVGRenderContext&,
+                           SkSTArray<2, SkScalar, true>*,
+                           SkSTArray<2, SkColor, true>*) const;
+
+    SkSVGLength fX1 = SkSVGLength(0  , SkSVGLength::Unit::kPercentage);
+    SkSVGLength fY1 = SkSVGLength(0  , SkSVGLength::Unit::kPercentage);
+    SkSVGLength fX2 = SkSVGLength(100, SkSVGLength::Unit::kPercentage);
+    SkSVGLength fY2 = SkSVGLength(0  , SkSVGLength::Unit::kPercentage);
+
+    SkSVGStringType fHref;
+
+    typedef SkSVGHiddenContainer INHERITED;
+};
+
+#endif // SkSVGLinearGradient_DEFINED