system_wrappers: rename interface -> include

webrtc/system_wrappers/interface/field_trial_default.h

-//
-// Copyright (c) 2015 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 WEBRTC_SYSTEM_WRAPPERS_INTERFACE_FIELD_TRIAL_DEFAULT_H_
-#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_FIELD_TRIAL_DEFAULT_H_
-
-namespace webrtc {
-namespace field_trial {
-
-// Optionally initialize field trial from a string.
-// This method can be called at most once before any other call into webrtc.
-// E.g. before the peer connection factory is constructed.
-// Note: trials_string must never be destroyed.
-void InitFieldTrialsFromString(const char* trials_string);
-
-}  // namespace field_trial
-}  // namespace webrtc
-
-#endif  // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_FIELD_TRIAL_DEFAULT_H_