Add //chromeos dependency in //extensions/browser/api/networking_private

extensions/browser/api/networking_private/BUILD.gn

 # Copyright 2016 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.
 
 import("//build/config/features.gni")
 
 source_set("networking_private") {
   sources = [
     "networking_cast_private_delegate.cc",
     "networking_cast_private_delegate.h",
     "networking_private_api.cc",
     "networking_private_api.h",
-    "networking_private_chromeos.cc",
-    "networking_private_chromeos.h",
     "networking_private_delegate.cc",
     "networking_private_delegate.h",
     "networking_private_delegate_factory.cc",
     "networking_private_delegate_factory.h",
     "networking_private_delegate_observer.h",
     "networking_private_event_router.h",
-    "networking_private_event_router_chromeos.cc",
     "networking_private_event_router_factory.cc",
     "networking_private_event_router_factory.h",
   ]
 
   deps = [
     "//extensions/common/api",
   ]
 
   if (!is_chromeos && is_linux) {
     sources += [
       "network_config_dbus_constants_linux.cc",
       "network_config_dbus_constants_linux.h",
       "networking_private_event_router_nonchromeos.cc",
       "networking_private_linux.cc",
       "networking_private_linux.h",
     ]
     if (use_dbus) {
       deps += [ "//dbus" ]
     }
   } else if (is_win || is_mac) {
     sources += [
       "networking_private_event_router_nonchromeos.cc",
       "networking_private_service_client.cc",
       "networking_private_service_client.h",
     ]
     deps += [ "//components/wifi" ]
+  } else if (is_chromeos) {
+    sources += [
+      "networking_private_chromeos.cc",
+      "networking_private_chromeos.h",
+      "networking_private_event_router_chromeos.cc",
+    ]
+    deps += [ "//chromeos" ]
   }
 }