Move MockVideoDecoder to api/test.

Move MockVideoDecoder from
modules/video_coding/include/mock/mock_video_codec_interface.h
to
api/test/mock_video_decoder.h

The mock encoder has already moved:
https://webrtc-review.googlesource.com/c/src/+/105620

Keeping the old header until downstream projects have been updated.

Bug: webrtc:9722
Change-Id: I4bc849173a04813064212f17761876695ca3fed4
Reviewed-on: https://webrtc-review.googlesource.com/c/105900
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25170}
diff --git a/api/BUILD.gn b/api/BUILD.gn
index 0727d82..ac3e308 100644
--- a/api/BUILD.gn
+++ b/api/BUILD.gn
@@ -517,7 +517,24 @@
     ]
   }
 
+  rtc_source_set("mock_video_decoder") {
+    visibility = [ "*" ]
+
+    testonly = true
+    sources = [
+      "test/mock_video_decoder.cc",
+      "test/mock_video_decoder.h",
+    ]
+
+    deps = [
+      "../api/video_codecs:video_codecs_api",
+      "../test:test_support",
+    ]
+  }
+
   rtc_source_set("mock_video_encoder") {
+    visibility = [ "*" ]
+
     testonly = true
     sources = [
       "test/mock_video_encoder.cc",
diff --git a/api/test/mock_video_decoder.cc b/api/test/mock_video_decoder.cc
new file mode 100644
index 0000000..85ed0e1
--- /dev/null
+++ b/api/test/mock_video_decoder.cc
@@ -0,0 +1,20 @@
+/*
+ *  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.
+ */
+
+#include "api/test/mock_video_decoder.h"
+
+namespace webrtc {
+
+MockDecodedImageCallback::MockDecodedImageCallback() = default;
+MockDecodedImageCallback::~MockDecodedImageCallback() = default;
+MockVideoDecoder::MockVideoDecoder() = default;
+MockVideoDecoder::~MockVideoDecoder() = default;
+
+}  // namespace webrtc
diff --git a/api/test/mock_video_decoder.h b/api/test/mock_video_decoder.h
new file mode 100644
index 0000000..56ff546
--- /dev/null
+++ b/api/test/mock_video_decoder.h
@@ -0,0 +1,57 @@
+/*
+ *  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_MOCK_VIDEO_DECODER_H_
+#define API_TEST_MOCK_VIDEO_DECODER_H_
+
+#include "api/video_codecs/video_decoder.h"
+#include "test/gmock.h"
+
+namespace webrtc {
+
+class MockDecodedImageCallback : public DecodedImageCallback {
+ public:
+  MockDecodedImageCallback();
+  ~MockDecodedImageCallback() override;
+
+  MOCK_METHOD1(Decoded, int32_t(VideoFrame& decodedImage));  // NOLINT
+  MOCK_METHOD2(Decoded,
+               int32_t(VideoFrame& decodedImage,  // NOLINT
+                       int64_t decode_time_ms));
+  MOCK_METHOD3(Decoded,
+               void(VideoFrame& decodedImage,  // NOLINT
+                    absl::optional<int32_t> decode_time_ms,
+                    absl::optional<uint8_t> qp));
+  MOCK_METHOD1(ReceivedDecodedReferenceFrame,
+               int32_t(const uint64_t pictureId));
+  MOCK_METHOD1(ReceivedDecodedFrame, int32_t(const uint64_t pictureId));
+};
+
+class MockVideoDecoder : public VideoDecoder {
+ public:
+  MockVideoDecoder();
+  ~MockVideoDecoder() override;
+
+  MOCK_METHOD2(InitDecode,
+               int32_t(const VideoCodec* codecSettings, int32_t numberOfCores));
+  MOCK_METHOD4(Decode,
+               int32_t(const EncodedImage& inputImage,
+                       bool missingFrames,
+                       const CodecSpecificInfo* codecSpecificInfo,
+                       int64_t renderTimeMs));
+  MOCK_METHOD1(RegisterDecodeCompleteCallback,
+               int32_t(DecodedImageCallback* callback));
+  MOCK_METHOD0(Release, int32_t());
+  MOCK_METHOD0(Copy, VideoDecoder*());
+};
+
+}  // namespace webrtc
+
+#endif  // API_TEST_MOCK_VIDEO_DECODER_H_