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

include/core/SkColorShader.h

Index: include/core/SkColorShader.h
diff --git a/include/core/SkColorShader.h b/include/core/SkColorShader.h
index 975156c0eb3a9e10120a02a92070030a72d3912e..56e5add4a31a446667ed5c121f92432de9f80657 100644
--- a/include/core/SkColorShader.h
+++ b/include/core/SkColorShader.h
@@ -30,16 +30,35 @@ public:
     */
     SkColorShader(SkColor c);
 
-    virtual ~SkColorShader();
-
-    virtual uint32_t getFlags() SK_OVERRIDE;
-    virtual uint8_t getSpan16Alpha() const SK_OVERRIDE;
     virtual bool isOpaque() const SK_OVERRIDE;
-    virtual bool setContext(const SkBitmap& device, const SkPaint& paint,
-                            const SkMatrix& matrix) SK_OVERRIDE;
-    virtual void shadeSpan(int x, int y, SkPMColor span[], int count) SK_OVERRIDE;
-    virtual void shadeSpan16(int x, int y, uint16_t span[], int count) SK_OVERRIDE;
-    virtual void shadeSpanAlpha(int x, int y, uint8_t alpha[], int count) SK_OVERRIDE;
+
+    virtual SkShader::Context* createContext(const SkBitmap& device,
+                                             const SkPaint& paint,
+                                             const SkMatrix& matrix,
+                                             void* storage) const SK_OVERRIDE;
+
+    virtual size_t contextSize() const SK_OVERRIDE {
+        return sizeof(ColorShaderContext);
+    }
+
+    class ColorShaderContext : public SkShader::Context {
+    public:
+        ColorShaderContext(const SkColorShader& shader, const SkBitmap& device,
+                           const SkPaint& paint, const SkMatrix& matrix);
+
+        virtual uint32_t getFlags() const SK_OVERRIDE;
+        virtual uint8_t getSpan16Alpha() const SK_OVERRIDE;
+        virtual void shadeSpan(int x, int y, SkPMColor span[], int count) SK_OVERRIDE;
+        virtual void shadeSpan16(int x, int y, uint16_t span[], int count) SK_OVERRIDE;
+        virtual void shadeSpanAlpha(int x, int y, uint8_t alpha[], int count) SK_OVERRIDE;
+
+    private:
+        SkPMColor   fPMColor;
+        uint32_t    fFlags;
+        uint16_t    fColor16;
+
+        typedef SkShader::Context INHERITED;
+    };
 
     // we return false for this, use asAGradient
     virtual BitmapType asABitmap(SkBitmap* outTexture,
@@ -56,11 +75,7 @@ protected:
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
 private:
-
     SkColor     fColor;         // ignored if fInheritColor is true
-    SkPMColor   fPMColor;       // cached after setContext()
-    uint32_t    fFlags;         // cached after setContext()
-    uint16_t    fColor16;       // cached after setContext()
     SkBool8     fInheritColor;
 
     typedef SkShader INHERITED;