Move GrTextContext to private interface

gyp/gpu.gyp

 {
   'target_defaults': {
     'conditions': [
       ['skia_os != "win"', {
         'sources/': [ ['exclude', '_win.(h|cpp)$'],
         ],
       }],
       ['skia_os != "mac"', {
         'sources/': [ ['exclude', '_mac.(h|cpp|m|mm)$'],
         ],
@@ skipping 121 matching lines @@
           'sources': [
             '../experimental/ChromeUtils/SkBorder.cpp',
             '../experimental/ChromeUtils/SkBorder.h',
           ],
           'defines': [
             'GR_CHROME_UTILS=1',
           ],
         }],
         [ 'skia_distancefield_fonts', {
           'sources': [
-            '<(skia_include_path)/gpu/GrDistanceFieldTextContext.h',
+            '<(skia_src_path)/gpu/GrDistanceFieldTextContext.h',
             '<(skia_src_path)/gpu/GrDistanceFieldTextContext.cpp',
             '<(skia_src_path)/gpu/effects/GrDistanceFieldTextureEffect.cpp',
             '<(skia_src_path)/gpu/effects/GrDistanceFieldTextureEffect.h',
           ],
           'defines': [
             'GR_DISTANCEFIELD_FONTS=1',
           ],
         }],
         [ 'skia_os == "linux" or skia_os == "chromeos"', {
           'sources!': [
@@ skipping 75 matching lines @@
             'libraries': [
               '-lGLESv2',
               '-lEGL',
             ],
           },
         }],
       ],
     },
   ],
 }