LibYuv GN: Add GN test targets.

libyuv.gni

+# Copyright 2016 The LibYuv Project Authors. All rights reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS. All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+import("//build_overrides/build.gni")
+import("//build/config/arm.gni")

[fbarchard1, 2016/09/12 18:59:45]

should include mips.gni for android?

[kjellander_chromium, 2016/09/12 20:14:57]

It's only needed if we're going to use any of the mipsel_* variables in
https://cs.chromium.org/chromium/src/build/config/mips.gni, which we currently
don't need (GYP isn't).

+
+declare_args() {
+  libyuv_include_tests = !build_with_chromium
+  libyuv_disable_jpeg = false
+  libyuv_use_neon = (current_cpu == "arm64" ||
+      (current_cpu == "arm" && (arm_use_neon || arm_optionally_use_neon)))
+}