[SVGDom] Initial linear gradient support

Kind of a big change, to connect several new bits into something useful:

  * ID tracking & lookup
  * new asPaint() node virtual to support shader (and in the future filter) based paint servers
  * <defs>, <linearGradient> and <stop> element support
  * 'href', 'offset', 'stop-color', 'stop-opacity' attribute support
  * IRI/FuncIRI and rgb(...) parsing

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2327233003

Review-Url: https://codereview.chromium.org/2327233003

1 files changed, 12 insertions, 4 deletions

diff --git a/experimental/svg/model/SkSVGTypes.h b/experimental/svg/model/SkSVGTypes.h
index 18ec3ce3cf..b2343a15e4 100644
--- a/experimental/svg/model/SkSVGTypes.h
+++ b/experimental/svg/model/SkSVGTypes.h
@@ -13,6 +13,7 @@
 #include "SkPoint.h"
 #include "SkRect.h"
 #include "SkScalar.h"
+#include "SkString.h"
 #include "SkTDArray.h"
 #include "SkTypes.h"
 
@@ -42,6 +43,7 @@ private:
 
 using SkSVGColorType      = SkSVGPrimitiveTypeWrapper<SkColor >;
 using SkSVGNumberType     = SkSVGPrimitiveTypeWrapper<SkScalar>;
+using SkSVGStringType     = SkSVGPrimitiveTypeWrapper<SkString>;
 using SkSVGViewBoxType    = SkSVGPrimitiveTypeWrapper<SkRect  >;
 using SkSVGTransformType  = SkSVGPrimitiveTypeWrapper<SkMatrix>;
 using SkSVGPointsType     = SkSVGPrimitiveTypeWrapper<SkTDArray<SkPoint>>;
@@ -88,27 +90,33 @@ public:
         kCurrentColor,
         kColor,
         kInherit,
+        kIRI,
     };
 
-    constexpr SkSVGPaint() : fType(Type::kInherit), fColor(SK_ColorBLACK) {}
-    explicit constexpr SkSVGPaint(Type t) : fType(t), fColor(SK_ColorBLACK) {}
-    explicit constexpr SkSVGPaint(const SkSVGColorType& c) : fType(Type::kColor), fColor(c) {}
+    SkSVGPaint() : fType(Type::kInherit), fColor(SK_ColorBLACK) {}
+    explicit SkSVGPaint(Type t) : fType(t), fColor(SK_ColorBLACK) {}
+    explicit SkSVGPaint(const SkSVGColorType& c) : fType(Type::kColor), fColor(c) {}
+    explicit SkSVGPaint(const SkString& iri)
+        : fType(Type::kIRI), fColor(SK_ColorBLACK), fIRI(iri) {}
 
     SkSVGPaint(const SkSVGPaint&)            = default;
     SkSVGPaint& operator=(const SkSVGPaint&) = default;
 
     bool operator==(const SkSVGPaint& other) const {
-        return fType == other.fType && fColor == other.fColor;
+        return fType == other.fType && fColor == other.fColor && fIRI == other.fIRI;
     }
     bool operator!=(const SkSVGPaint& other) const { return !(*this == other); }
 
     Type type() const { return fType; }
     const SkSVGColorType& color() const { SkASSERT(fType == Type::kColor); return fColor; }
+    const SkString& iri() const { SkASSERT(fType == Type::kIRI); return fIRI; }
 
 private:
     Type fType;
 
+    // Logical union.
     SkSVGColorType fColor;
+    SkString       fIRI;
 };
 
 class SkSVGLineCap {