Revert[6] "move some public headers into private"

gyp/sfnt.gyp

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 {
   'targets': [
     {
       'target_name': 'sfnt',
       'product_name': 'skia_sfnt',
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [
         'core.gyp:*',
       ],
       'include_dirs': [
+        '../src/core',
         '../src/sfnt',
       ],
       'sources': [
         '../src/sfnt/SkIBMFamilyClass.h',
         '../src/sfnt/SkOTTableTypes.h',
         '../src/sfnt/SkOTTable_EBDT.h',
         '../src/sfnt/SkOTTable_EBLC.h',
         '../src/sfnt/SkOTTable_EBSC.h',
         '../src/sfnt/SkOTTable_gasp.h',
         '../src/sfnt/SkOTTable_glyf.h',
@@ skipping 23 matching lines @@
         '../src/sfnt/SkOTUtils.cpp',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../src/sfnt',
         ],
       },
     },
   ],
 }