Added API for Bevel NormalSource.

src/core/SkNormalFlatSource.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 SkNormalFlatSource_DEFINED
+#define SkNormalFlatSource_DEFINED
+
+#include "SkNormalSource.h"
+
+class SK_API SkNormalFlatSourceImpl : public SkNormalSource {
+public:
+    SkNormalFlatSourceImpl(){}
+
+#if SK_SUPPORT_GPU
+    sk_sp<GrFragmentProcessor> asFragmentProcessor(const SkShader::AsFPArgs&) const override;
+#endif
+
+    SkNormalSource::Provider* asProvider(const SkShader::ContextRec& rec,
+                                         void* storage) const override;
+    size_t providerSize(const SkShader::ContextRec& rec) const override;
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkNormalFlatSourceImpl)
+
+protected:
+    void flatten(SkWriteBuffer& buf) const override;
+
+private:
+    class Provider : public SkNormalSource::Provider {
+    public:
+        Provider();
+
+        virtual ~Provider();
+
+        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
+
+    private:
+        typedef SkNormalSource::Provider INHERITED;
+    };
+
+    friend class SkNormalSource;
+
+    typedef SkNormalSource INHERITED;
+};
+
+#endif