Added API for Bevel NormalSource.

src/core/SkNormalSource.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 SkNormalSource_DEFINED
 #define SkNormalSource_DEFINED
 
 #include "SkFlattenable.h"
+#include "SkShader.h"
+
+class SkMatrix;
+struct SkPoint3;
+
+#if SK_SUPPORT_GPU
+class GrFragmentProcessor;
+#endif
 
 /** Abstract class that generates or reads in normals for use by SkLightingShader.
 */
 class SK_API SkNormalSource : public SkFlattenable {
 public:
     virtual ~SkNormalSource() override;
 
 #if SK_SUPPORT_GPU
     /** Returns a fragment processor that takes no input and outputs a normal (already rotated)
         as its output color. To be used as a child fragment processor.
@@ skipping 35 matching lines @@
             N.normalize();
         The +Z axis is thus encoded in RGB as (127, 127, 255) while the -Z axis is
         (127, 127, 0).
     */
     static sk_sp<SkNormalSource> MakeFromNormalMap(sk_sp<SkShader> map, const SkMatrix& ctm);
 
     /** Returns a normal source that provides straight-up normals only (0, 0, 1).
     */
     static sk_sp<SkNormalSource> MakeFlat();
 
+    /** This enum specifies the shape of the bevel. All bevels output <0, 0, 1> as the surface
+     *  normal for any point more than 'width' away from any edge.
+     *
+     *  Mathematical details:
+     *  For the purpose of describing the shape of the bevel, we define 'w' to be the given width of
+     *  the bevel, and 'h' to be the given height. We will assume the shape is rotated such that the
+     *  point being shaded as well as the closest point in the shape's edge to that point are in the
+     *  x-axis, and the shape is translated so that the aforementioned point in the edge is at
+     *  coordinates (w, 0, 0) and the end of the bevel is at (0, 0, h).
+     *
+     */
+    enum class BevelType {
+        /* This bevel simulates a surface that is slanted from the shape's edges inwards, linearly.
+         *
+         * Mathematical details:
+         * This bevel follows a straight line from (w, 0, 0) to (0, 0, h).
+         */
+        kLinear,
+        /* This bevel simulates a surface that rounds off at the shape's edges, smoothly becoming
+         * perpendicular to the x-y plane.
+         *
+         * Mathematical details:
+         * This bevel follows the only quadratic bezier curve whose start point is at (w, 0, 0),
+         * control point is at (w, 0, h), and end point is at (0, 0, h).
+         */
+        kRoundedOut,
+        /* This bevel simulates a surface that sharply becomes perpendicular to the x-y plane when
+         * at 'width' units from the nearest edge, and then rounds off towards the shape's
+         * edge, smoothly becoming parallel to the x-y plane.
+         *
+         * Mathematical details:
+         * This bevel follows the only quadratic bezier curve whose start point is at (w, 0, 0),
+         * control point is at (0, 0, 0), and end point is at (0, 0, h).
+         */
+        kRoundedIn
+    };
+    /** Returns a normal source that generates a bevel for the given shape. UNIMPLEMENTED: Will
+        return straight-up normals only.
+
+        @param  type   the type of bevel to add
+        @param  width  the width of the bevel, in source space. Must be positive.
+        @param  height the height of the plateau, in source space. Can be positive, negative,
+                       or zero. A negative height means the simulated bevels slope downwards.
+    */
+    static sk_sp<SkNormalSource> MakeBevel(BevelType, SkScalar width, SkScalar height);
+
     SK_DEFINE_FLATTENABLE_TYPE(SkNormalSource)
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 };
 
 #endif