pdf: Create a separate component for using the pdf pepper plugin.

components/components.gyp

 # Copyright (c) 2013 The Chromium 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': {
     # This turns on e.g. the filename-based detection of which
     # platforms to include source files on (e.g. files ending in
     # _mac.h or _mac.cc are only compiled on MacOSX).
     'chromium_code': 1,
@@ skipping 92 matching lines @@
       # introduced.
       'includes': [
         'gcm_driver.gypi',
         'omnibox.gypi',
         'renderer_context_menu.gypi',
         'search_engines.gypi',
         'sync_driver.gypi',
         'invalidation.gypi',
       ],
     }],
+    ['enable_plugins==1', {
+      'includes': [
+        'pdf.gypi',
+      ],
+    }],
   ],
 }