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

This also makes the Note at the top of the files (to keep the GYP and
GN files in sync) a bit more noticeable.

BUG=

Review URL: https://codereview.chromium.org/1116463002

Cr-Commit-Position: refs/heads/master@{#327378}

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': {

remoting/webapp/files.gni

@@ -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/remoting_webapp_files.gypi.
+# `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/remoting_webapp_files.gypi.
 
 # Jscompile proto files.
 # These provide type information for jscompile.
@@ -216,6 +224,7 @@ remoting_webapp_js_host_control_files = [
 remoting_webapp_js_host_display_files = [
   "crd/js/host_list.js",
   "crd/js/host_list_api.js",
+  "crd/js/host_list_api_gcd_impl.js",
   "crd/js/host_list_api_impl.js",
   "crd/js/host_table_entry.js",
   "crd/js/local_host_section.js",