Factor out checkerboard function in gm and sampleapp into tools.

gyp/gmslides.gypi

 # include this gypi to include all the golden master slides.
 {
   'include_dirs': [
     '../gm',
     # include dirs needed by particular GMs
     '../src/utils/debugger',
     '../src/images',
     '../src/lazy',
   ],
   'conditions': [
@@ skipping 180 matching lines @@
         '../gm/textblob.cpp',
         '../gm/textblobshader.cpp',
         '../gm/texturedomaineffect.cpp',
         '../gm/thinrects.cpp',
         '../gm/thinstrokedrects.cpp',
         '../gm/tiledscaledbitmap.cpp',
         '../gm/tileimagefilter.cpp',
         '../gm/tilemodes.cpp',
         '../gm/tilemodes_scaled.cpp',
         '../gm/tinybitmap.cpp',
+        '../gm/transparency.cpp',
         '../gm/twopointradial.cpp',
         '../gm/typeface.cpp',
         '../gm/vertices.cpp',
         '../gm/verttext.cpp',
         '../gm/verttext2.cpp',
         '../gm/verylargebitmap.cpp',
         '../gm/xfermodeimagefilter.cpp',
         '../gm/xfermodes.cpp',
         '../gm/xfermodes2.cpp',
         '../gm/xfermodes3.cpp',
         '../gm/yuvtorgbeffect.cpp',
 
         # Files needed by particular GMs
+        '../gm/checkerboard.h',
+        '../gm/checkerboard.cpp',
         '../src/utils/debugger/SkDrawCommand.h',
         '../src/utils/debugger/SkDrawCommand.cpp',
         '../src/utils/debugger/SkDebugCanvas.h',
         '../src/utils/debugger/SkDebugCanvas.cpp',
         '../src/utils/debugger/SkObjectParser.h',
         '../src/utils/debugger/SkObjectParser.cpp',
       ],
     }],
     # TODO: Several GMs are known to cause particular problems on Android, so
     # we disable them on Android.  See http://skbug.com/2326
@@ skipping 20 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',
       ],
     }],
   ],
 }