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diff --git a/third_party/libwebrtc/sdk/media_constraints.cc b/third_party/libwebrtc/sdk/media_constraints.cc
new file mode 100644
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+++ b/third_party/libwebrtc/sdk/media_constraints.cc
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+/*
+ *  Copyright 2013 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 "sdk/media_constraints.h"
+
+#include "absl/types/optional.h"
+#include "api/peer_connection_interface.h"
+
+namespace webrtc {
+namespace {
+
+// Find the highest-priority instance of the T-valued constraint named by
+// `key` and return its value as `value`. `constraints` can be null.
+// If `mandatory_constraints` is non-null, it is incremented if the key appears
+// among the mandatory constraints.
+// Returns true if the key was found and has a valid value for type T.
+// If the key appears multiple times as an optional constraint, appearances
+// after the first are ignored.
+// Note: Because this uses FindFirst, repeated optional constraints whose
+// first instance has an unrecognized value are not handled precisely in
+// accordance with the specification.
+template <typename T>
+bool FindConstraint(const MediaConstraints* constraints,
+                    const std::string& key,
+                    T* value,
+                    size_t* mandatory_constraints) {
+  std::string string_value;
+  if (!FindConstraint(constraints, key, &string_value, mandatory_constraints)) {
+    return false;
+  }
+  return rtc::FromString(string_value, value);
+}
+
+// Specialization for std::string, since a string doesn't need conversion.
+template <>
+bool FindConstraint(const MediaConstraints* constraints,
+                    const std::string& key,
+                    std::string* value,
+                    size_t* mandatory_constraints) {
+  if (!constraints) {
+    return false;
+  }
+  if (constraints->GetMandatory().FindFirst(key, value)) {
+    if (mandatory_constraints) {
+      ++*mandatory_constraints;
+    }
+    return true;
+  }
+  if (constraints->GetOptional().FindFirst(key, value)) {
+    return true;
+  }
+  return false;
+}
+
+bool FindConstraint(const MediaConstraints* constraints,
+                    const std::string& key,
+                    bool* value,
+                    size_t* mandatory_constraints) {
+  return FindConstraint<bool>(constraints, key, value, mandatory_constraints);
+}
+
+bool FindConstraint(const MediaConstraints* constraints,
+                    const std::string& key,
+                    int* value,
+                    size_t* mandatory_constraints) {
+  return FindConstraint<int>(constraints, key, value, mandatory_constraints);
+}
+
+// Converts a constraint (mandatory takes precedence over optional) to an
+// absl::optional.
+template <typename T>
+void ConstraintToOptional(const MediaConstraints* constraints,
+                          const std::string& key,
+                          absl::optional<T>* value_out) {
+  T value;
+  bool present = FindConstraint<T>(constraints, key, &value, nullptr);
+  if (present) {
+    *value_out = value;
+  }
+}
+}  // namespace
+
+const char MediaConstraints::kValueTrue[] = "true";
+const char MediaConstraints::kValueFalse[] = "false";
+
+// Constraints declared as static members in mediastreaminterface.h
+
+// Audio constraints.
+const char MediaConstraints::kGoogEchoCancellation[] = "googEchoCancellation";
+const char MediaConstraints::kAutoGainControl[] = "googAutoGainControl";
+const char MediaConstraints::kNoiseSuppression[] = "googNoiseSuppression";
+const char MediaConstraints::kHighpassFilter[] = "googHighpassFilter";
+const char MediaConstraints::kAudioMirroring[] = "googAudioMirroring";
+const char MediaConstraints::kAudioNetworkAdaptorConfig[] =
+    "googAudioNetworkAdaptorConfig";
+const char MediaConstraints::kInitAudioRecordingOnSend[] =
+    "InitAudioRecordingOnSend";
+
+// Constraint keys for CreateOffer / CreateAnswer defined in W3C specification.
+const char MediaConstraints::kOfferToReceiveAudio[] = "OfferToReceiveAudio";
+const char MediaConstraints::kOfferToReceiveVideo[] = "OfferToReceiveVideo";
+const char MediaConstraints::kVoiceActivityDetection[] =
+    "VoiceActivityDetection";
+const char MediaConstraints::kIceRestart[] = "IceRestart";
+// Google specific constraint for BUNDLE enable/disable.
+const char MediaConstraints::kUseRtpMux[] = "googUseRtpMUX";
+
+// Below constraints should be used during PeerConnection construction.
+// Google-specific constraint keys.
+const char MediaConstraints::kEnableDscp[] = "googDscp";
+const char MediaConstraints::kEnableVideoSuspendBelowMinBitrate[] =
+    "googSuspendBelowMinBitrate";
+const char MediaConstraints::kCombinedAudioVideoBwe[] =
+    "googCombinedAudioVideoBwe";
+const char MediaConstraints::kScreencastMinBitrate[] =
+    "googScreencastMinBitrate";
+// TODO(ronghuawu): Remove once cpu overuse detection is stable.
+const char MediaConstraints::kCpuOveruseDetection[] = "googCpuOveruseDetection";
+
+const char MediaConstraints::kRawPacketizationForVideoEnabled[] =
+    "googRawPacketizationForVideoEnabled";
+
+const char MediaConstraints::kNumSimulcastLayers[] = "googNumSimulcastLayers";
+
+// Set `value` to the value associated with the first appearance of `key`, or
+// return false if `key` is not found.
+bool MediaConstraints::Constraints::FindFirst(const std::string& key,
+                                              std::string* value) const {
+  for (Constraints::const_iterator iter = begin(); iter != end(); ++iter) {
+    if (iter->key == key) {
+      *value = iter->value;
+      return true;
+    }
+  }
+  return false;
+}
+
+void CopyConstraintsIntoRtcConfiguration(
+    const MediaConstraints* constraints,
+    PeerConnectionInterface::RTCConfiguration* configuration) {
+  // Copy info from constraints into configuration, if present.
+  if (!constraints) {
+    return;
+  }
+
+  FindConstraint(constraints, MediaConstraints::kEnableDscp,
+                 &configuration->media_config.enable_dscp, nullptr);
+  FindConstraint(constraints, MediaConstraints::kCpuOveruseDetection,
+                 &configuration->media_config.video.enable_cpu_adaptation,
+                 nullptr);
+  // Find Suspend Below Min Bitrate constraint.
+  FindConstraint(
+      constraints, MediaConstraints::kEnableVideoSuspendBelowMinBitrate,
+      &configuration->media_config.video.suspend_below_min_bitrate, nullptr);
+  ConstraintToOptional<int>(constraints,
+                            MediaConstraints::kScreencastMinBitrate,
+                            &configuration->screencast_min_bitrate);
+  ConstraintToOptional<bool>(constraints,
+                             MediaConstraints::kCombinedAudioVideoBwe,
+                             &configuration->combined_audio_video_bwe);
+}
+
+void CopyConstraintsIntoAudioOptions(const MediaConstraints* constraints,
+                                     cricket::AudioOptions* options) {
+  if (!constraints) {
+    return;
+  }
+
+  ConstraintToOptional<bool>(constraints,
+                             MediaConstraints::kGoogEchoCancellation,
+                             &options->echo_cancellation);
+  ConstraintToOptional<bool>(constraints, MediaConstraints::kAutoGainControl,
+                             &options->auto_gain_control);
+  ConstraintToOptional<bool>(constraints, MediaConstraints::kNoiseSuppression,
+                             &options->noise_suppression);
+  ConstraintToOptional<bool>(constraints, MediaConstraints::kHighpassFilter,
+                             &options->highpass_filter);
+  ConstraintToOptional<bool>(constraints, MediaConstraints::kAudioMirroring,
+                             &options->stereo_swapping);
+  ConstraintToOptional<std::string>(
+      constraints, MediaConstraints::kAudioNetworkAdaptorConfig,
+      &options->audio_network_adaptor_config);
+  // When `kAudioNetworkAdaptorConfig` is defined, it both means that audio
+  // network adaptor is desired, and provides the config string.
+  if (options->audio_network_adaptor_config) {
+    options->audio_network_adaptor = true;
+  }
+  ConstraintToOptional<bool>(constraints,
+                             MediaConstraints::kInitAudioRecordingOnSend,
+                             &options->init_recording_on_send);
+}
+
+bool CopyConstraintsIntoOfferAnswerOptions(
+    const MediaConstraints* constraints,
+    PeerConnectionInterface::RTCOfferAnswerOptions* offer_answer_options) {
+  if (!constraints) {
+    return true;
+  }
+
+  bool value = false;
+  size_t mandatory_constraints_satisfied = 0;
+
+  if (FindConstraint(constraints, MediaConstraints::kOfferToReceiveAudio,
+                     &value, &mandatory_constraints_satisfied)) {
+    offer_answer_options->offer_to_receive_audio =
+        value ? PeerConnectionInterface::RTCOfferAnswerOptions::
+                    kOfferToReceiveMediaTrue
+              : 0;
+  }
+
+  if (FindConstraint(constraints, MediaConstraints::kOfferToReceiveVideo,
+                     &value, &mandatory_constraints_satisfied)) {
+    offer_answer_options->offer_to_receive_video =
+        value ? PeerConnectionInterface::RTCOfferAnswerOptions::
+                    kOfferToReceiveMediaTrue
+              : 0;
+  }
+  if (FindConstraint(constraints, MediaConstraints::kVoiceActivityDetection,
+                     &value, &mandatory_constraints_satisfied)) {
+    offer_answer_options->voice_activity_detection = value;
+  }
+  if (FindConstraint(constraints, MediaConstraints::kUseRtpMux, &value,
+                     &mandatory_constraints_satisfied)) {
+    offer_answer_options->use_rtp_mux = value;
+  }
+  if (FindConstraint(constraints, MediaConstraints::kIceRestart, &value,
+                     &mandatory_constraints_satisfied)) {
+    offer_answer_options->ice_restart = value;
+  }
+
+  if (FindConstraint(constraints,
+                     MediaConstraints::kRawPacketizationForVideoEnabled, &value,
+                     &mandatory_constraints_satisfied)) {
+    offer_answer_options->raw_packetization_for_video = value;
+  }
+
+  int layers;
+  if (FindConstraint(constraints, MediaConstraints::kNumSimulcastLayers,
+                     &layers, &mandatory_constraints_satisfied)) {
+    offer_answer_options->num_simulcast_layers = layers;
+  }
+
+  return mandatory_constraints_satisfied == constraints->GetMandatory().size();
+}
+
+}  // namespace webrtc