Add SkColor4f serialization

tools/debugger/SkJsonWriteBuffer.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkJsonWriteBuffer_DEFINED
 #define SkJsonWriteBuffer_DEFINED
 
@@ skipping 17 matching lines @@
     void writeScalar(SkScalar value) override;
     void writeScalarArray(const SkScalar* value, uint32_t count) override;
     void writeInt(int32_t value) override;
     void writeIntArray(const int32_t* value, uint32_t count) override;
     void writeUInt(uint32_t value) override;
     void writeString(const char* value) override;
 
     void writeFlattenable(const SkFlattenable* flattenable) override;
     void writeColor(SkColor color) override;
     void writeColorArray(const SkColor* color, uint32_t count) override;
+    void writeColor4f(const SkColor4f& color) override;
+    void writeColor4fArray(const SkColor4f* color, uint32_t count) override;
     void writePoint(const SkPoint& point) override;
     void writePointArray(const SkPoint* point, uint32_t count) override;
     void writeMatrix(const SkMatrix& matrix) override;
     void writeIRect(const SkIRect& rect) override;
     void writeRect(const SkRect& rect) override;
     void writeRegion(const SkRegion& region) override;
     void writePath(const SkPath& path) override;
     size_t writeStream(SkStream* stream, size_t length) override;
     void writeBitmap(const SkBitmap& bitmap) override;
     void writeImage(const SkImage*) override;
     void writeTypeface(SkTypeface* typeface) override;
     void writePaint(const SkPaint& paint) override;
 
     const Json::Value& getValue() const { return fJson; }
 
 private:
     void append(const char* type, const Json::Value& value);
 
     UrlDataManager* fUrlDataManager;
     Json::Value fJson;
 };
 
 #endif