add -Iinclude/private anywhere we have -Isrc/core

gyp/pdfviewer_lib.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.
 # GYP file to build pdfviewer.
 #
 # To build on Linux:
 #  ./gyp_skia pdfviewer.gyp && make pdfviewer
 #
 {
@@ skipping 27 matching lines @@
         '../experimental/PdfViewer/pdfparser/native/pdfapi/SkPdfMapper_autogen.cpp',
         '../experimental/PdfViewer/pdfparser/native/pdfapi/SkPdfHeaders_autogen.cpp',
       ],
       'include_dirs': [
         '../experimental/PdfViewer',
         '../experimental/PdfViewer/inc',
         '../experimental/PdfViewer/src',
         '../experimental/PdfViewer/pdfparser',
         '../experimental/PdfViewer/pdfparser/native',
         '../experimental/PdfViewer/pdfparser/native/pdfapi',
+        '../include/private',
         '../src/core',
       ],
       'dependencies': [
         'skia_lib.gyp:skia_lib',
         'skflate.gyp:skflate',
       ],
     },
   ],
 }