Add frame_helpers

A number of utility functions to be shared between frame buffer 2
and the new frame scheduling implementation based on frame buffer 3.

Change-Id: Icc932c6c76fddeeedc8aa64ec27c7e0c955abfd0
Bug: webrtc:13343
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/241604
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35743}

modules/video_coding/frame_helpers.h

@@ -0,0 +1,31 @@
+/*
+ *  Copyright (c) 2021 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 MODULES_VIDEO_CODING_FRAME_HELPERS_H_
+#define MODULES_VIDEO_CODING_FRAME_HELPERS_H_
+
+#include <memory>
+
+#include "absl/container/inlined_vector.h"
+#include "api/video/encoded_frame.h"
+
+namespace webrtc {
+
+// TODO(https://bugs.webrtc.org/13589): Switch to using Timestamp and TimeDelta.
+bool FrameHasBadRenderTiming(int64_t render_time_ms,
+                             int64_t now_ms,
+                             int target_video_delay);
+
+std::unique_ptr<EncodedFrame> CombineAndDeleteFrames(
+    absl::InlinedVector<std::unique_ptr<EncodedFrame>, 4> frames);
+
+}  // namespace webrtc
+
+#endif  // MODULES_VIDEO_CODING_FRAME_HELPERS_H_