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
 
@@ skipping 51 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();
 
+    enum class BevelType {

[egdaniel, 2016/07/14 17:23:30]

Can you add comment on what these different BevelTypes mean.

[dvonbeck, 2016/07/19 23:00:13]

Do you know if I can change my source file's encoding to UTF? I'd like to do
stuff like ◜¯¯¯¯◝ or ◝------◜ in the comments to make it easier to visualize the
different types.

[egdaniel, 2016/07/19 23:31:26]

I wouldn't change the encoding. Just describe in mathematical words and folks
should be able to understand. 

Also I was thinking the other day that cubic bevels would also be nice. With
them we can have C1 continuity of the edges with but the surface and the top of
the object.

[dvonbeck, 2016/07/22 15:08:22]

Done.

+        kLinear,
+        kRoundedOut,
+        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
+        @param  height the height of the plateau, in source space
+    */
+    static sk_sp<SkNormalSource> MakeBevel(BevelType, SkScalar width, SkScalar height);

[egdaniel, 2016/07/14 17:23:30]

We need more info in the comments here. What happens with bevels that are much
wider than the shape? Can the bevels be negative? Can the height be negative
(inward sloping things).

[dvonbeck, 2016/07/22 15:08:22]

Done.

+
     SK_DEFINE_FLATTENABLE_TYPE(SkNormalSource)
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 };
 
 #endif