Factor out checkerboard function in gm and sampleapp into tools.

gyp/tools.gyp

     # GYP file to build various tools.
 #
 # To build on Linux:
 #  ./gyp_skia tools.gyp && make tools
 #
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
@@ skipping 88 matching lines @@
       'dependencies': [
         'resources',
         'flags.gyp:flags',
         'skia_lib.gyp:skia_lib',
       ],
       'direct_dependent_settings': {
         'include_dirs': [ '../tools', ],
       },
     },
     {
+      'target_name': 'checkerboard',
+      'type': 'static_library',
+      'sources': [ '../tools/Checkerboard.cpp', ],
+      'dependencies': [ 'skia_lib.gyp:skia_lib', ],
+      'direct_dependent_settings': { 'include_dirs': [ '../tools', ], },
+    },
+    {
       'target_name' : 'timer',
       'type': 'static_library',
       'sources': [
         '../tools/timer/Timer.cpp',
         '../tools/timer/TimerData.cpp',
       ],
       'include_dirs': [
         '../src/core',
         '../src/gpu',
       ],
@@ skipping 653 matching lines @@
               'flags.gyp:flags',
               'skia_lib.gyp:skia_lib',
               'resources',
             ],
           },
         ],
       },
     ],
   ],
 }