Fix all relative includes to third_party.

third_party/third_party.gyp

 # Copyright 2014 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'target_defaults': {
     'defines': [
       'OPJ_STATIC',
       '_CRT_SECURE_NO_WARNINGS',
     ],
+    'include_dirs': [
+      # This is implicit in GN.
+      '<(DEPTH)',
+      '..',
+    ],
     'msvs_disabled_warnings': [
       4005, 4018, 4146, 4333, 4345, 4267
     ],
   },
   'targets': [
     {
       'target_name': 'bigint',
       'type': 'static_library',
       'sources': [
         'bigint/BigInteger.hh',
@@ skipping 133 matching lines @@
       ],
       'variables': {
         'clang_warning_flags': [
           '-Wno-missing-braces',
           # FindPrev() in cmsplugin.c is unused.
           '-Wno-unused-function',
         ],
       },
     },
     {
-      'target_name': 'fx_libjpeg',
+      'target_name': 'libjpeg',
       'type': 'static_library',
       'sources': [
         'libjpeg/cderror.h',
         'libjpeg/cdjpeg.h',
         'libjpeg/fpdfapi_jcapimin.c',
         'libjpeg/fpdfapi_jcapistd.c',
         'libjpeg/fpdfapi_jccoefct.c',
         'libjpeg/fpdfapi_jccolor.c',
         'libjpeg/fpdfapi_jcdctmgr.c',
         'libjpeg/fpdfapi_jchuff.c',
@@ skipping 110 matching lines @@
         'base/numerics/safe_conversions.h',
         'base/numerics/safe_conversions_impl.h',
         'base/numerics/safe_math.h',
         'base/numerics/safe_math_impl.h',
         'base/stl_util.h',
         'base/template_util.h',
       ],
     },
   ],
 }