Add StereoCodecAdapter classes

This CL is the step 1 for adding alpha channel support over the wire in webrtc.
- Add the footprint for adapter classes that wraps actual codecs.
- This CL does not add a webrtc::VideoFrame container that can carry alpha to 
make the CL shorter for an easier review. Therefore, it exercises a code path
for when we receive no alpha input, just regular I420 frames.
- Unittest sends a video frame for encode/decode through these adapters and 
checks the output PSNR.
- See https://webrtc-review.googlesource.com/c/src/+/7800 for the experimental 
CL that gives an idea about how it will come together.
Design Doc: https://goo.gl/sFeSUT

Bug: webrtc:7671
Change-Id: I9d3be13647a0a958feceb8d7a9aa93852fc6a1fa
Reviewed-on: https://webrtc-review.googlesource.com/11841
Commit-Queue: Emircan Uysaler <emircan@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Niklas Enbom <niklas.enbom@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20490}

modules/video_coding/codecs/stereo/test/stereo_adapter_unittest.cc

@@ -0,0 +1,96 @@
+/*
+ *  Copyright (c) 2017 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.
+ */
+
+#include "api/test/mock_video_decoder_factory.h"
+#include "api/test/mock_video_encoder_factory.h"
+#include "common_video/libyuv/include/webrtc_libyuv.h"
+#include "modules/video_coding/codecs/stereo/include/stereo_decoder_adapter.h"
+#include "modules/video_coding/codecs/stereo/include/stereo_encoder_adapter.h"
+#include "modules/video_coding/codecs/test/video_codec_test.h"
+#include "modules/video_coding/codecs/vp9/include/vp9.h"
+
+using testing::_;
+using testing::Return;
+
+namespace webrtc {
+
+class TestStereoAdapter : public VideoCodecTest {
+ public:
+  TestStereoAdapter()
+      : decoder_factory_(new webrtc::MockVideoDecoderFactory),
+        encoder_factory_(new webrtc::MockVideoEncoderFactory) {}
+
+ protected:
+  VideoDecoder* CreateDecoder() override {
+    return new StereoDecoderAdapter(decoder_factory_.get());
+  }
+
+  VideoEncoder* CreateEncoder() override {
+    return new StereoEncoderAdapter(encoder_factory_.get());
+  }
+
+  VideoCodec codec_settings() override {
+    VideoCodec codec_settings;
+    codec_settings.codecType = webrtc::kVideoCodecVP9;
+    codec_settings.VP9()->numberOfTemporalLayers = 1;
+    codec_settings.VP9()->numberOfSpatialLayers = 1;
+    return codec_settings;
+  }
+
+ private:
+  void SetUp() override {
+    EXPECT_CALL(*decoder_factory_, Die());
+    VideoDecoder* decoder1 = VP9Decoder::Create();
+    VideoDecoder* decoder2 = VP9Decoder::Create();
+    EXPECT_CALL(*decoder_factory_, CreateVideoDecoderProxy(_))
+        .WillOnce(Return(decoder1))
+        .WillOnce(Return(decoder2));
+
+    EXPECT_CALL(*encoder_factory_, Die());
+    VideoEncoder* encoder1 = VP9Encoder::Create();
+    VideoEncoder* encoder2 = VP9Encoder::Create();
+    EXPECT_CALL(*encoder_factory_, CreateVideoEncoderProxy(_))
+        .WillOnce(Return(encoder1))
+        .WillOnce(Return(encoder2));
+
+    VideoCodecTest::SetUp();
+  }
+
+  const std::unique_ptr<webrtc::MockVideoDecoderFactory> decoder_factory_;
+  const std::unique_ptr<webrtc::MockVideoEncoderFactory> encoder_factory_;
+};
+
+// TODO(emircan): Currently VideoCodecTest tests do a complete setup
+// step that goes beyond constructing |decoder_|. Simplify these tests to do
+// less.
+TEST_F(TestStereoAdapter, ConstructAndDestructDecoder) {
+  EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK, decoder_->Release());
+}
+
+TEST_F(TestStereoAdapter, ConstructAndDestructEncoder) {
+  EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK, encoder_->Release());
+}
+
+TEST_F(TestStereoAdapter, EncodeDecodeI420Frame) {
+  EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK,
+            encoder_->Encode(*input_frame_, nullptr, nullptr));
+  EncodedImage encoded_frame;
+  CodecSpecificInfo codec_specific_info;
+  ASSERT_TRUE(WaitForEncodedFrame(&encoded_frame, &codec_specific_info));
+  EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK,
+            decoder_->Decode(encoded_frame, false, nullptr));
+  std::unique_ptr<VideoFrame> decoded_frame;
+  rtc::Optional<uint8_t> decoded_qp;
+  ASSERT_TRUE(WaitForDecodedFrame(&decoded_frame, &decoded_qp));
+  ASSERT_TRUE(decoded_frame);
+  EXPECT_GT(I420PSNR(input_frame_.get(), decoded_frame.get()), 36);
+}
+
+}  // namespace webrtc