Allow building non-XFA (master) on the XFA branch.

samples/samples.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.
 
 {
   'variables': {
     'pdf_enable_v8%': 1,
+    'pdf_enable_xfa%': 1,
   },
   'target_defaults': {
     'defines' : [
       'PNG_PREFIX',
       'PNGPREFIX_H',
       'PNG_USE_READ_MACROS',
     ],
     'include_dirs': [
       # This is implicit in GN.
       '<(DEPTH)',
       '..',
     ],
     'conditions': [
       ['pdf_enable_v8==1', {
         'defines': [
           'PDF_ENABLE_V8',
         ],
         'include_dirs': [
           '<(DEPTH)/v8',
           '<(DEPTH)/v8/include',
         ],
       }],
+      ['pdf_enable_xfa==1', {
+        'defines': [
+          'PDF_ENABLE_XFA',
+        ],
+      }],
     ],
   },
   'targets': [
     {
       'target_name': 'pdfium_test',
       'type': 'executable',
       'dependencies': [
         '../pdfium.gyp:pdfium',
         '../pdfium.gyp:test_support',
         # Regardless of whether the library ships against system freetype,
         # always link this binary against the bundled one for consistency
         # of results across platforms.
         '../third_party/third_party.gyp:fx_freetype',
       ],
       'sources': [
         'pdfium_test.cc',
         'image_diff_png.cc',
       ],
       'link_settings': {
         'libraries!': [
           '-lfreetype',
         ],
       },
       'conditions': [
+        ['pdf_enable_xfa==0', {
+          'dependencies': [
+            '../third_party/third_party.gyp:fx_lpng',
+          ],
+        }],
         ['pdf_enable_v8==1', {
           'dependencies': [
             '<(DEPTH)/v8/tools/gyp/v8.gyp:v8_libplatform',
           ],
         }],
       ],
     },
     {
       'target_name': 'pdfium_diff',
       'type': 'executable',
       'variables': { 'enable_wexit_time_destructors': 1, },
       'dependencies': [
         '../pdfium.gyp:pdfium',
         '../third_party/third_party.gyp:pdfium_base',
       ],
       'sources': [
         'image_diff.cc',
         'image_diff_png.h',
         'image_diff_png.cc',
       ],
+      'conditions': [
+        ['pdf_enable_xfa==0', {
+          'dependencies': [
+            '../third_party/third_party.gyp:fx_lpng',
+          ],
+        }],
+      ],
     },
   ],
 }