third_party: Add libevdev and gestures.

third_party/libevdev/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/linux/pkg_config.gni")
+
+assert(is_linux)
+
+declare_args() {
+  # Controls whether the build should use the version of libevdev
+  # library shipped with the system. In release builds of Chrome OS we
+  # use the system version, but when building on dev workstations we
+  # bundle it because Ubuntu doesn't ship a usable version.
+  use_system_libevdev = true
+}
+
+if (!use_system_libevdev) {
+  config("libevdev_config") {
+    include_dirs = [ "src/include" ]
+  }
+
+  static_library("libevdev") {
+    sources = [
+      "src/src/libevdev.c",
+      "src/src/libevdev_event.c",
+      "src/src/libevdev_mt.c",
+    ]
+
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += [ "//build/config/compiler:no_chromium_code" ]
+
+    public_configs = [ ":libevdev_config" ]
+  }
+}
+
+if (use_system_libevdev) {
+  pkg_config("libevdev-cros") {
+    packages = [ "libevdev-cros" ]
+  }
+
+  group("libevdev") {
+    public_configs = [ ":libevdev-cros" ]
+  }
+}