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

src/effects/gradients/SkTwoPointConicalGradient.h

Index: src/effects/gradients/SkTwoPointConicalGradient.h
diff --git a/src/effects/gradients/SkTwoPointConicalGradient.h b/src/effects/gradients/SkTwoPointConicalGradient.h
index b2e258ee68b277bfce6e99ce1d4f179df0d9f2dc..80aa6fa6939ab3559cc9827df3fa5536718f7db0 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient.h
+++ b/src/effects/gradients/SkTwoPointConicalGradient.h
@@ -11,6 +11,8 @@
 
 #include "SkGradientShaderPriv.h"
 
+// TODO(dominikg): Worth making it truly immutable (i.e. set values in constructor)?
+// Should only be initialized once via init(). Immutable afterwards.
 struct TwoPtRadial {
     enum {
         kDontDrawT  = 0x80000000
@@ -29,13 +31,6 @@
               const SkPoint& center1, SkScalar rad1,
               bool flipped);
 
-    // used by setup and nextT
-    float   fRelX, fRelY, fIncX, fIncY;
-    float   fB, fDB;
-
-    void setup(SkScalar fx, SkScalar fy, SkScalar dfx, SkScalar dfy);
-    SkFixed nextT();
-
     static bool DontDrawT(SkFixed t) {
         return kDontDrawT == (uint32_t)t;
     }
@@ -51,11 +46,24 @@
                               const SkPoint& end, SkScalar endRadius,
                               bool flippedGrad, const Descriptor&);
 
-    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 SkShader::Context* createContext(const SkBitmap&, const SkPaint&, const SkMatrix&,
+                                             void* storage) const SK_OVERRIDE;
+    virtual size_t contextSize() const SK_OVERRIDE;
+
+    class TwoPointConicalGradientContext : public SkGradientShaderBase::GradientShaderBaseContext {
+    public:
+        TwoPointConicalGradientContext(const SkTwoPointConicalGradient& shader,
+                                       const SkBitmap& device,
+                                       const SkPaint& paint,
+                                       const SkMatrix& matrix);
+        ~TwoPointConicalGradientContext() {}
+
+        virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;
+
+    private:
+        typedef SkGradientShaderBase::GradientShaderBaseContext INHERITED;
+    };
 
     virtual BitmapType asABitmap(SkBitmap* bitmap,
                                  SkMatrix* matrix,