Generic 4f gradient T sampler fallback

src/effects/gradients/Sk4fLinearGradient.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 Sk4fLinearGradient_DEFINED
 #define Sk4fLinearGradient_DEFINED
 
 #include "Sk4fGradientBase.h"
 #include "SkLinearGradient.h"
 
 class SkLinearGradient::
-LinearGradient4fContext : public GradientShaderBase4fContext {
+LinearGradient4fContext final : public GradientShaderBase4fContext {
 public:
     LinearGradient4fContext(const SkLinearGradient&, const ContextRec&);
 
     void shadeSpan(int x, int y, SkPMColor dst[], int count) override;
     void shadeSpan4f(int x, int y, SkPM4f dst[], int count) override;
 
+protected:
+    void mapTs(int x, int y, SkScalar ts[], int count) const override;
+
 private:
     using INHERITED = GradientShaderBase4fContext;
 
-    void addMirrorIntervals(const SkLinearGradient&, const Sk4f& componentScale,
-                            bool dx_is_pos);
-
     template<typename DstType, TileMode>
     class LinearIntervalProcessor;
 
     template <typename DstType, bool premul>
     void shadePremulSpan(int x, int y, DstType[], int count) const;
 
     template <typename DstType, bool premul, SkShader::TileMode tileMode>
-    void shadePremulTileSpan(int x, int y, DstType[], int count) const;
-
-    template <typename DstType, bool premul, SkShader::TileMode tileMode>
     void shadeSpanInternal(int x, int y, DstType[], int count) const;
 
     const Interval* findInterval(SkScalar fx) const;
 
+    bool isFast() const { return fDstToPosClass == kLinear_MatrixClass; }
+
     mutable const Interval*      fCachedInterval;
 };
 
 #endif // Sk4fLinearGradient_DEFINED