move colorshader into its own .cpp, add color4f variant

src/core/SkColorShader.h

Index: src/core/SkColorShader.h
diff --git a/src/core/SkColorShader.h b/src/core/SkColorShader.h
index db71b6ef9fdc4cb6f12c12d7afa56e5b36de3d5d..f7e609498b8a96347b6bf44e6f2e08a11f164bb8 100644
--- a/src/core/SkColorShader.h
+++ b/src/core/SkColorShader.h
@@ -72,4 +72,60 @@ private:
     typedef SkShader INHERITED;
 };
 
+class SkColor4Shader : public SkShader {
+public:
+    SkColor4Shader(const SkColor4f&, sk_sp<SkColorSpace>);
+
+    bool isOpaque() const override {
+        return SkColorGetA(fCachedByteColor) == 255;
+    }
+
+    class Color4Context : public SkShader::Context {
+    public:
+        Color4Context(const SkColor4Shader& shader, const ContextRec&);
+
+        uint32_t getFlags() const override;
+        void shadeSpan(int x, int y, SkPMColor span[], int count) override;
+        void shadeSpanAlpha(int x, int y, uint8_t alpha[], int count) override;
+        void shadeSpan4f(int x, int y, SkPM4f[], int count) override;
+
+    protected:
+        bool onChooseBlitProcs(const SkImageInfo&, BlitState*) override;
+
+    private:
+        SkPM4f      fPM4f;
+        SkPMColor   fPMColor;
+        uint32_t    fFlags;
+
+        typedef SkShader::Context INHERITED;
+    };
+
+    GradientType asAGradient(GradientInfo* info) const override;
+
+#if SK_SUPPORT_GPU
+    const GrFragmentProcessor* asFragmentProcessor(GrContext*, const SkMatrix& viewM,
+                                                   const SkMatrix*, SkFilterQuality) const override;
+#endif
+
+    SK_TO_STRING_OVERRIDE()
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkColorShader)
+
+protected:
+    SkColor4Shader(SkReadBuffer&);
+    void flatten(SkWriteBuffer&) const override;
+    Context* onCreateContext(const ContextRec&, void* storage) const override;
+    size_t onContextSize(const ContextRec&) const override { return sizeof(Color4Context); }
+    bool onAsLuminanceColor(SkColor* lum) const override {
+        *lum = fCachedByteColor;
+        return true;
+    }
+
+private:
+    sk_sp<SkColorSpace> fColorSpace;
+    const SkColor4f     fColor4;
+    const SkColor       fCachedByteColor;
+    
+    typedef SkShader INHERITED;
+};
+
 #endif