add 4f support to colorfiltershader

src/core/SkColorFilterShader.h

Index: src/core/SkColorFilterShader.h
diff --git a/src/core/SkColorFilterShader.h b/src/core/SkColorFilterShader.h
index e92908ee83dd421649f9ca28ae547216e31496c9..55625b69919c3fbd5ba5b1d53191ff63bab7f955 100644
--- a/src/core/SkColorFilterShader.h
+++ b/src/core/SkColorFilterShader.h
@@ -33,7 +33,8 @@ public:
         uint32_t getFlags() const override;
         
         void shadeSpan(int x, int y, SkPMColor[], int count) override;
-        
+        void shadeSpan4f(int x, int y, SkPM4f[], int count) override;
+
         void set3DMask(const SkMask* mask) override {
             // forward to our proxy
             fShaderContext->set3DMask(mask);