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+//
+// 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>
+
+#include "webrtc/common_types.h"
+
+// 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/source/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_