Start extraction of frame_generator_capturer.h|cc into separate target

Introduce temporary header for downstream projects to migrate on a
separate target.

Bug: b/272350185
Change-Id: Ibeeae48395af4d7a06371b2d6d7ffc861dc479f2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/300864
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39821}
diff --git a/test/BUILD.gn b/test/BUILD.gn
index b50a203..f3be88a 100644
--- a/test/BUILD.gn
+++ b/test/BUILD.gn
@@ -126,6 +126,13 @@
   ]
 }
 
+rtc_library("frame_generator_capturer") {
+  visibility = [ "*" ]
+  testonly = true
+  sources = [ "frame_generator_capturer_tmp.h" ]
+  deps = [ ":video_test_common" ]
+}
+
 rtc_library("video_test_common") {
   visibility = [ "*" ]
   testonly = true
diff --git a/test/frame_generator_capturer_tmp.h b/test/frame_generator_capturer_tmp.h
new file mode 100644
index 0000000..69e0cf5
--- /dev/null
+++ b/test/frame_generator_capturer_tmp.h
@@ -0,0 +1,16 @@
+/*
+ *  Copyright (c) 2023 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 TEST_FRAME_GENERATOR_CAPTURER_TMP_H_
+#define TEST_FRAME_GENERATOR_CAPTURER_TMP_H_
+
+#include "test/frame_generator_capturer.h"
+
+#endif  // TEST_FRAME_GENERATOR_CAPTURER_TMP_H_