system_wrappers: rename interface -> include

webrtc/system_wrappers/interface/field_trial.h

-//
-// Copyright (c) 2014 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_H_
-#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_FIELD_TRIAL_H_
-
-#include <string>
-
-// Field trials allow webrtc clients (such as Chrome) to turn on feature code
-// in binaries out in the field and gather information with that.
-//
-// WebRTC clients MUST provide an implementation of:
-//
-//   std::string webrtc::field_trial::FindFullName(const std::string& trial).
-//
-// Or link with a default one provided in:
-//
-//   system_wrappers/system_wrappers.gyp:field_trial_default
-//
-//
-// They are designed to wire up directly to chrome field trials and to speed up
-// developers by reducing the need to wire APIs to control whether a feature is
-// on/off. E.g. to experiment with a new method that could lead to a different
-// trade-off between CPU/bandwidth:
-//
-// 1 - Develop the feature with default behaviour off:
-//
-//   if (FieldTrial::FindFullName("WebRTCExperimenMethod2") == "Enabled")
-//     method2();
-//   else
-//     method1();
-//
-// 2 - Once the changes are rolled to chrome, the new code path can be
-//     controlled as normal chrome field trials.
-//
-// 3 - Evaluate the new feature and clean the code paths.
-//
-// Notes:
-//   - NOT every feature is a candidate to be controlled by this mechanism as
-//     it may require negotation between involved parties (e.g. SDP).
-//
-// TODO(andresp): since chrome --force-fieldtrials does not marks the trial
-//     as active it does not gets propaged to renderer process. For now one
-//     needs to push a config with start_active:true or run a local finch
-//     server.
-//
-// TODO(andresp): find out how to get bots to run tests with trials enabled.
-
-namespace webrtc {
-namespace field_trial {
-
-// Returns the group name chosen for the named trial, or the empty string
-// if the trial does not exists.
-//
-// Note: To keep things tidy append all the trial names with WebRTC.
-std::string FindFullName(const std::string& name);
-
-}  // namespace field_trial
-}  // namespace webrtc
-
-#endif  // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_FIELD_TRIAL_H_