[webnfc] Add WebNFC feature flag

chrome/browser/flag_descriptions.cc

 // Copyright 2017 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.
 
 #include "chrome/browser/flag_descriptions.h"
 
 namespace flag_descriptions {
 
 //  Material Design version of chrome://bookmarks
 
@@ skipping 3009 matching lines @@
 
 const char kEnableCopylessPasteName[] = "App Indexing (Copyless Paste)";
 
 const char kEnableCopylessPasteDescription[] =
     "Provide suggestions for text input, based on your recent context. For "
     "example, if you looked at a restaurant website and switched to the Maps "
     "app, the keyboard would offer the name of that restaurant as a suggestion "
     "to enter into the search bar. The data is indexed locally, and never sent "
     "to the server. It's disabled in incognito mode.";
 
+const char kEnableWebNfcName[] = "WebNFC";
+
+const char kEnableWebNfcDescription[] = "Enable WebNFC support.";
+
 #endif  // defined(OS_ANDROID)
 
 }  // namespace flag_descriptions