add a GM to demo the blend bug

gyp/gmslides.gypi

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 # include this gypi to include all the golden master slides.
 {
   'include_dirs': [
     '../gm',
     # include dirs needed by particular GMs
     '../src/utils/debugger',
@@ skipping 24 matching lines @@
         '../gm/bitmapcopy.cpp',
         '../gm/bitmapfilters.cpp',
         '../gm/bitmappremul.cpp',
         '../gm/bitmaprect.cpp',
         '../gm/bitmaprecttest.cpp',
         '../gm/bitmapscroll.cpp',
         '../gm/bitmapshader.cpp',
         '../gm/bitmapsource.cpp',
         '../gm/bitmapsource2.cpp',
         '../gm/bleed.cpp',
+        '../gm/blend.cpp',
         '../gm/blurcircles.cpp',
         '../gm/blurs.cpp',
         '../gm/blurquickreject.cpp',
         '../gm/blurrect.cpp',
         '../gm/blurroundrect.cpp',
         '../gm/bmpfilterqualityrepeat.cpp',
         '../gm/circles.cpp',
         '../gm/circularclips.cpp',
         '../gm/clipdrawdraw.cpp',
         '../gm/clip_strokerect.cpp',
@@ skipping 216 matching lines @@
         '../gm/shadertext2.cpp',
         '../gm/shadertext3.cpp',
 
         # TODO(reed): Allocates more memory than Android devices are capable of
         # fulfilling. See http://skbug.com/1978
         '../gm/verylargebitmap.cpp',
       ],
     }],
   ],
 }