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diff --git a/third_party/libwebrtc/api/audio/channel_layout.h b/third_party/libwebrtc/api/audio/channel_layout.h
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+/*
+ *  Copyright (c) 2019 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_AUDIO_CHANNEL_LAYOUT_H_
+#define API_AUDIO_CHANNEL_LAYOUT_H_
+
+namespace webrtc {
+
+// This file is derived from Chromium's base/channel_layout.h.
+
+// Enumerates the various representations of the ordering of audio channels.
+// Logged to UMA, so never reuse a value, always add new/greater ones!
+enum ChannelLayout {
+  CHANNEL_LAYOUT_NONE = 0,
+  CHANNEL_LAYOUT_UNSUPPORTED = 1,
+
+  // Front C
+  CHANNEL_LAYOUT_MONO = 2,
+
+  // Front L, Front R
+  CHANNEL_LAYOUT_STEREO = 3,
+
+  // Front L, Front R, Back C
+  CHANNEL_LAYOUT_2_1 = 4,
+
+  // Front L, Front R, Front C
+  CHANNEL_LAYOUT_SURROUND = 5,
+
+  // Front L, Front R, Front C, Back C
+  CHANNEL_LAYOUT_4_0 = 6,
+
+  // Front L, Front R, Side L, Side R
+  CHANNEL_LAYOUT_2_2 = 7,
+
+  // Front L, Front R, Back L, Back R
+  CHANNEL_LAYOUT_QUAD = 8,
+
+  // Front L, Front R, Front C, Side L, Side R
+  CHANNEL_LAYOUT_5_0 = 9,
+
+  // Front L, Front R, Front C, LFE, Side L, Side R
+  CHANNEL_LAYOUT_5_1 = 10,
+
+  // Front L, Front R, Front C, Back L, Back R
+  CHANNEL_LAYOUT_5_0_BACK = 11,
+
+  // Front L, Front R, Front C, LFE, Back L, Back R
+  CHANNEL_LAYOUT_5_1_BACK = 12,
+
+  // Front L, Front R, Front C, Side L, Side R, Back L, Back R
+  CHANNEL_LAYOUT_7_0 = 13,
+
+  // Front L, Front R, Front C, LFE, Side L, Side R, Back L, Back R
+  CHANNEL_LAYOUT_7_1 = 14,
+
+  // Front L, Front R, Front C, LFE, Side L, Side R, Front LofC, Front RofC
+  CHANNEL_LAYOUT_7_1_WIDE = 15,
+
+  // Stereo L, Stereo R
+  CHANNEL_LAYOUT_STEREO_DOWNMIX = 16,
+
+  // Stereo L, Stereo R, LFE
+  CHANNEL_LAYOUT_2POINT1 = 17,
+
+  // Stereo L, Stereo R, Front C, LFE
+  CHANNEL_LAYOUT_3_1 = 18,
+
+  // Stereo L, Stereo R, Front C, Rear C, LFE
+  CHANNEL_LAYOUT_4_1 = 19,
+
+  // Stereo L, Stereo R, Front C, Side L, Side R, Back C
+  CHANNEL_LAYOUT_6_0 = 20,
+
+  // Stereo L, Stereo R, Side L, Side R, Front LofC, Front RofC
+  CHANNEL_LAYOUT_6_0_FRONT = 21,
+
+  // Stereo L, Stereo R, Front C, Rear L, Rear R, Rear C
+  CHANNEL_LAYOUT_HEXAGONAL = 22,
+
+  // Stereo L, Stereo R, Front C, LFE, Side L, Side R, Rear Center
+  CHANNEL_LAYOUT_6_1 = 23,
+
+  // Stereo L, Stereo R, Front C, LFE, Back L, Back R, Rear Center
+  CHANNEL_LAYOUT_6_1_BACK = 24,
+
+  // Stereo L, Stereo R, Side L, Side R, Front LofC, Front RofC, LFE
+  CHANNEL_LAYOUT_6_1_FRONT = 25,
+
+  // Front L, Front R, Front C, Side L, Side R, Front LofC, Front RofC
+  CHANNEL_LAYOUT_7_0_FRONT = 26,
+
+  // Front L, Front R, Front C, LFE, Back L, Back R, Front LofC, Front RofC
+  CHANNEL_LAYOUT_7_1_WIDE_BACK = 27,
+
+  // Front L, Front R, Front C, Side L, Side R, Rear L, Back R, Back C.
+  CHANNEL_LAYOUT_OCTAGONAL = 28,
+
+  // Channels are not explicitly mapped to speakers.
+  CHANNEL_LAYOUT_DISCRETE = 29,
+
+  // Front L, Front R, Front C. Front C contains the keyboard mic audio. This
+  // layout is only intended for input for WebRTC. The Front C channel
+  // is stripped away in the WebRTC audio input pipeline and never seen outside
+  // of that.
+  CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC = 30,
+
+  // Front L, Front R, Side L, Side R, LFE
+  CHANNEL_LAYOUT_4_1_QUAD_SIDE = 31,
+
+  // Actual channel layout is specified in the bitstream and the actual channel
+  // count is unknown at Chromium media pipeline level (useful for audio
+  // pass-through mode).
+  CHANNEL_LAYOUT_BITSTREAM = 32,
+
+  // Max value, must always equal the largest entry ever logged.
+  CHANNEL_LAYOUT_MAX = CHANNEL_LAYOUT_BITSTREAM
+};
+
+// Note: Do not reorder or reassign these values; other code depends on their
+// ordering to operate correctly. E.g., CoreAudio channel layout computations.
+enum Channels {
+  LEFT = 0,
+  RIGHT,
+  CENTER,
+  LFE,
+  BACK_LEFT,
+  BACK_RIGHT,
+  LEFT_OF_CENTER,
+  RIGHT_OF_CENTER,
+  BACK_CENTER,
+  SIDE_LEFT,
+  SIDE_RIGHT,
+  CHANNELS_MAX =
+      SIDE_RIGHT,  // Must always equal the largest value ever logged.
+};
+
+// The maximum number of concurrently active channels for all possible layouts.
+// ChannelLayoutToChannelCount() will never return a value higher than this.
+constexpr int kMaxConcurrentChannels = 8;
+
+// Returns the expected channel position in an interleaved stream.  Values of -1
+// mean the channel at that index is not used for that layout.  Values range
+// from 0 to ChannelLayoutToChannelCount(layout) - 1.
+int ChannelOrder(ChannelLayout layout, Channels channel);
+
+// Returns the number of channels in a given ChannelLayout.
+int ChannelLayoutToChannelCount(ChannelLayout layout);
+
+// Given the number of channels, return the best layout,
+// or return CHANNEL_LAYOUT_UNSUPPORTED if there is no good match.
+ChannelLayout GuessChannelLayout(int channels);
+
+// Returns a string representation of the channel layout.
+const char* ChannelLayoutToString(ChannelLayout layout);
+
+}  // namespace webrtc
+
+#endif  // API_AUDIO_CHANNEL_LAYOUT_H_