[Chromoting] Add missing file to webapp's GN build.

remoting/remoting_webapp_files.gypi

Index: remoting/remoting_webapp_files.gypi
diff --git a/remoting/remoting_webapp_files.gypi b/remoting/remoting_webapp_files.gypi
index 60d7b4bca05f2435f2fb0ccaf62bc27677601997..7312dc87d7b98a58cd2ebfeddfcfa2e5dabc8e58 100644
--- a/remoting/remoting_webapp_files.gypi
+++ b/remoting/remoting_webapp_files.gypi
@@ -2,7 +2,15 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# Keep in sync with remoting/webapp/files.gni.
+# `7MM"""Mq.                       `7MM
+#   MM   `MM.                        MM
+#   MM   ,M9  .gP"Ya   ,6"Yb.   ,M""bMM  `7MMpMMMb.pMMMb.  .gP"Ya
+#   MMmmdM9  ,M'   Yb 8)   MM ,AP    MM    MM    MM    MM ,M'   Yb
+#   MM  YM.  8M""""""  ,pm9MM 8MI    MM    MM    MM    MM 8M""""""
+#   MM   `Mb.YM.    , 8M   MM `Mb    MM    MM    MM    MM YM.    ,
+# .JMML. .JMM.`Mbmmd' `Moo9^Yo.`Wbmd"MML..JMML  JMML  JMML.`Mbmmd'
+#
+# Please keep this file in sync with remoting/webapp/files.gni.
 
 {
   'variables': {