Port chromevox build to GN.

chrome/third_party/chromevox/BUILD.gn

+# Copyright 2014 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.
+
+if (is_chromeos) {
+  import("//chrome/browser/resources/chromeos/chromevox/chromevox.gni")
+
+  group("chromevox_third_party_resources") {
+    deps = [
+      ":chromevox_third_party_background_resources",
+      ":chromevox_third_party_injected_resources",
+    ]
+  }
+
+  copy("chromevox_third_party_background_resources") {
+    sources = [
+      "chromevox/background/chrome_shared2.css",
+      "chromevox/background/options.css",
+      "chromevox/background/options_widgets.css",
+    ]
+    outputs = [
+      "$chromevox_out_dir/chromevox/background/{{source_file_part}}",
+    ]
+  }
+
+  copy("chromevox_third_party_injected_resources") {
+    sources = [
+      "chromevox/injected/mathjax.js",
+      "chromevox/injected/mathjax_external_util.js",
+    ]
+    outputs = [
+      "$chromevox_out_dir/chromevox/injected/{{source_file_part}}",
+    ]
+  }
+}