Adding third_party/openh264 build files for encoding

third_party/openh264/testing/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("//testing/test.gni")
+import("//third_party/openh264/openh264_args.gni")
+
+if (use_openh264) {
+  test("openh264_unittests") {
+    sources = [
+      "h264_codec_tester.cc",
+      "h264_codec_tester.h",
+      "h264_decoder_impl.cc",
+      "h264_decoder_impl.h",
+      "h264_encoder_impl.cc",
+      "h264_encoder_impl.h",
+      "i420_utils.cc",
+      "i420_utils.h",
+      "openh264_unittests.cc",
+    ]
+    defines = [ "INCLUDE_OPENH264_UNITTESTS" ]
+    deps = [
+      "//testing/gtest",
+      "//third_party/openh264:openh264_encoder",
+      "//third_party/openh264:openh264_decoder",
+      "//third_party/webrtc/common_video",
+    ]
+  }
+} else {
+  # When building without OpenH264 we still produce a test binary but it won't
+  # contain any tests.
+  test("openh264_unittests") {
+    sources = [
+      "openh264_unittests.cc",
+    ]
+    deps = [
+      "//testing/gtest",
+    ]
+  }
+}