rename SkBitmapChecksummer as SkBitmapHasher, and prepare for it to possibly use

gyp/tests.gyp

 # GYP file to build unit tests.
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
     {
       'target_name': 'tests',
       'type': 'executable',
       'include_dirs' : [
         '../src/core',
         '../src/effects',
         '../src/lazy',
         '../src/pdf',
         '../src/pipe/utils',
         '../src/utils',
         '../tools/',
       ],
       'sources': [
         '../tests/AAClipTest.cpp',
         '../tests/AnnotationTest.cpp',
         '../tests/AtomicTest.cpp',
         '../tests/BitmapCopyTest.cpp',
         '../tests/BitmapFactoryTest.cpp',
         '../tests/BitmapGetColorTest.cpp',
+        '../tests/BitmapHasherTest.cpp',
         '../tests/BitmapHeapTest.cpp',
         '../tests/BitmapTransformerTest.cpp',
         '../tests/BitSetTest.cpp',
         '../tests/BlitRowTest.cpp',
         '../tests/BlurTest.cpp',
         '../tests/CanvasTest.cpp',
         '../tests/ChecksumTest.cpp',
         '../tests/ClampRangeTest.cpp',
         '../tests/ClipCacheTest.cpp',
         '../tests/ClipCubicTest.cpp',
@@ skipping 100 matching lines @@
           'include_dirs': [
             '../src/gpu',
           ],
         }],
         [ 'skia_os == "nacl"', {
           # CityHash is not supported on NaCl because the NaCl toolchain is
           # missing byteswap.h which is needed by CityHash.
           # TODO(borenet): Find a way to either provide this dependency or
           # replace it.
           'sources!': [
+            '../tests/BitmapHasherTest.cpp',
             '../tests/ChecksumTest.cpp',
           ],
         }],
       ],
     },
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: