remove flags that control no code

gyp/pdf.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.
 # This file builds the PDF backend.
 {
   'targets': [
     {
       'target_name': 'pdf',
       'product_name': 'skia_pdf',
@@ skipping 27 matching lines @@
               'external/sfntly/cpp/src',
             ],
             'libraries': [
               'libsfntly.a',
               '-licuuc',
               '-licui18n',
             ],
           }
         ],
       ],
-      # This section makes all targets that depend on this target
-      # #define SK_SUPPORT_PDF and have access to the pdf header files.
       'direct_dependent_settings': {
-        'defines': [
-          'SK_SUPPORT_PDF',
-        ],
         'include_dirs': [
           '../include/core',  # SkDocument.h
         ],
       },
     },
   ],
 }