Adding third_party/openh264/src, build files and unittests

third_party/openh264/tests/openh264_unittests.cc

-// 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.
-
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace openh264 {
-
-class OpenH264Tests : public testing::Test {
-};
-
-TEST_F(OpenH264Tests, DummyTestAlwaysPass) {
-}
-
-}  // namespace openh264
-
-int main(int argc, char **argv) {
-  ::testing::InitGoogleTest(&argc, argv);
-  return RUN_ALL_TESTS();
-}