Implement some WiFi Display elementary stream descriptors.

extensions/extensions_tests.gyp

 {
   'includes': [
     'extensions_tests.gypi',
   ],
   'variables': {
     # Product name is used for Mac bundle.
     'app_shell_product_name': 'App Shell',
     # The version is high enough to be supported by Omaha (at least 31)
     # but fake enough to be obviously not a Chrome release.
     'app_shell_version': '38.1234.5678.9',
@@ skipping 43 matching lines @@
       'msvs_disabled_warnings': [ 4267, ],
       'conditions': [
         ['chromeos==1', {
           'dependencies': [
             '<(DEPTH)/chromeos/chromeos.gyp:chromeos_test_support',
           ],
           'sources': [
             'browser/api/webcam_private/visca_webcam_unittest.cc',
           ],
         }],
+        ['enable_wifi_display==1', {
+          'sources': [
+            '<@(extensions_unittests_sources_wifi_display)',
+          ],
+        }],
       ],
     },
     {
       # GN version: //extensions:extensions_browsertests
       'target_name': 'extensions_browsertests',
       'type': '<(gtest_target_type)',
       'dependencies': [
         'extensions.gyp:extensions_test_support',
         'shell/app_shell.gyp:app_shell_lib',
         # TODO(yoz): find the right deps
@@ skipping 67 matching lines @@
               'dependencies': [
                 '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
               ],
             }],
           ],
         }
       ],
     }],
   ],
 }