Port chromevox build to GN.

chrome/browser/resources/chromeos/braille_ime/BUILD.gn

 # Copyright 2015 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")
-
-if (enable_nacl && (is_linux || is_win)) {
-  executable("mock_nacl_gdb") {
+if (is_chromeos) {
+  copy("braille_ime_manifest") {
     sources = [
-      "mock_nacl_gdb.cc",
+      "manifest.json",
     ]
-    deps = [
-      "//base",
+    outputs = [
+      "$root_out_dir/resources/chromeos/braille_ime/manifest.json",
     ]
   }
 }