Publish function_video_(en|de)coder_factory into api

Bug: None
Change-Id: Ibdae580c085cfc4b063fdc7f1edb8312de438722
Reviewed-on: https://webrtc-review.googlesource.com/c/107705
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25360}

api/test/video/function_video_encoder_factory.h

@@ -0,0 +1,65 @@
+/*
+ *  Copyright (c) 2018 The WebRTC 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.
+ */
+
+#ifndef API_TEST_VIDEO_FUNCTION_VIDEO_ENCODER_FACTORY_H_
+#define API_TEST_VIDEO_FUNCTION_VIDEO_ENCODER_FACTORY_H_
+
+#include <functional>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "api/video_codecs/sdp_video_format.h"
+#include "api/video_codecs/video_encoder_factory.h"
+#include "rtc_base/checks.h"
+
+namespace webrtc {
+namespace test {
+
+// An encoder factory producing encoders by calling a supplied create
+// function.
+class FunctionVideoEncoderFactory final : public VideoEncoderFactory {
+ public:
+  explicit FunctionVideoEncoderFactory(
+      std::function<std::unique_ptr<VideoEncoder>()> create)
+      : create_([create](const SdpVideoFormat&) { return create(); }) {}
+  explicit FunctionVideoEncoderFactory(
+      std::function<std::unique_ptr<VideoEncoder>(const SdpVideoFormat&)>
+          create)
+      : create_(std::move(create)) {}
+
+  // Unused by tests.
+  std::vector<SdpVideoFormat> GetSupportedFormats() const override {
+    RTC_NOTREACHED();
+    return {};
+  }
+
+  CodecInfo QueryVideoEncoder(
+      const SdpVideoFormat& /* format */) const override {
+    CodecInfo codec_info;
+    codec_info.is_hardware_accelerated = false;
+    codec_info.has_internal_source = false;
+    return codec_info;
+  }
+
+  std::unique_ptr<VideoEncoder> CreateVideoEncoder(
+      const SdpVideoFormat& format) override {
+    return create_(format);
+  }
+
+ private:
+  const std::function<std::unique_ptr<VideoEncoder>(const SdpVideoFormat&)>
+      create_;
+};
+
+}  // namespace test
+}  // namespace webrtc
+
+#endif  // API_TEST_VIDEO_FUNCTION_VIDEO_ENCODER_FACTORY_H_