Extract most of the mutable state of SkShader into a separate Context object.

src/effects/gradients/SkTwoPointRadialGradient.h

Index: src/effects/gradients/SkTwoPointRadialGradient.h
diff --git a/src/effects/gradients/SkTwoPointRadialGradient.h b/src/effects/gradients/SkTwoPointRadialGradient.h
index ee1b49ee952ce52a79c36245c05a3aef69c0837c..84bc3f3ae52311bf8fb7bab27d174acf45b8c85f 100644
--- a/src/effects/gradients/SkTwoPointRadialGradient.h
+++ b/src/effects/gradients/SkTwoPointRadialGradient.h
@@ -23,11 +23,25 @@ public:
     virtual GradientType asAGradient(GradientInfo* info) const SK_OVERRIDE;
     virtual GrEffectRef* asNewEffect(GrContext* context, const SkPaint&) const SK_OVERRIDE;
 
-    virtual void shadeSpan(int x, int y, SkPMColor* dstCParam,
-                           int count) SK_OVERRIDE;
-    virtual bool setContext(const SkBitmap& device,
-                            const SkPaint& paint,
-                            const SkMatrix& matrix) SK_OVERRIDE;
+
+    virtual size_t contextSize() const SK_OVERRIDE;
+    bool validContext(const SkBitmap&, const SkPaint&, const SkMatrix&) const SK_OVERRIDE;
+    virtual SkShader::Context* createContext(const SkBitmap&, const SkPaint&, const SkMatrix&,
+                                             void* storage) const SK_OVERRIDE;
+
+    class TwoPointRadialGradientContext : public SkGradientShaderBase::GradientShaderBaseContext {
+    public:
+        TwoPointRadialGradientContext(const SkTwoPointRadialGradient& shader,
+                                      const SkBitmap& device,
+                                      const SkPaint& paint,
+                                      const SkMatrix& matrix);
+        ~TwoPointRadialGradientContext() {}
+
+        virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;
+
+    private:
+        typedef SkGradientShaderBase::GradientShaderBaseContext INHERITED;
+    };
 
     SkScalar getCenterX1() const { return fDiff.length(); }
     SkScalar getStartRadius() const { return fStartRadius; }
@@ -41,7 +55,6 @@ protected:
     virtual void flatten(SkWriteBuffer& buffer) const SK_OVERRIDE;
 
 private:
-    typedef SkGradientShaderBase INHERITED;
     const SkPoint fCenter1;
     const SkPoint fCenter2;
     const SkScalar fRadius1;
@@ -50,6 +63,8 @@ private:
     SkScalar fStartRadius, fDiffRadius, fSr2D2, fA, fOneOverTwoA;
 
     void init();
+
+    typedef SkGradientShaderBase INHERITED;
 };
 
 #endif