Moved ALR experiment settings to new experiments folder.

This replaces most of the existing dependencies on the application
limited region(ALR) detector. This is to achieve a greater separation of
concerns and will make further refactoring regarding the ALR Detector
less invasive on other parts of the code base.

Bug: webrtc:8415
Change-Id: I92912254c6d02285cce6a88f6789f0ac94794c88
Reviewed-on: https://webrtc-review.googlesource.com/37560
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21598}

rtc_base/experiments/BUILD.gn

@@ -0,0 +1,21 @@
+# Copyright (c) 2018 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.
+
+import("../../webrtc.gni")
+
+rtc_static_library("alr_experiment") {
+  sources = [
+    "alr_experiment.cc",
+    "alr_experiment.h",
+  ]
+  deps = [
+    "../:rtc_base_approved",
+    "../../api:optional",
+    "../../system_wrappers:field_trial_api",
+  ]
+}

rtc_base/experiments/DEPS

@@ -0,0 +1,3 @@
+include_rules = [
+  "+system_wrappers",
+]

rtc_base/experiments/alr_experiment.cc

@@ -0,0 +1,83 @@
+/*
+ *  Copyright (c) 2018 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 "rtc_base/experiments/alr_experiment.h"
+
+#include <string>
+
+#include "rtc_base/format_macros.h"
+#include "rtc_base/logging.h"
+#include "system_wrappers/include/field_trial.h"
+
+namespace webrtc {
+
+const char AlrExperimentSettings::kScreenshareProbingBweExperimentName[] =
+    "WebRTC-ProbingScreenshareBwe";
+const char AlrExperimentSettings::kStrictPacingAndProbingExperimentName[] =
+    "WebRTC-StrictPacingAndProbing";
+const char kDefaultProbingScreenshareBweSettings[] = "1.0,2875,80,40,-60,3";
+
+bool AlrExperimentSettings::MaxOneFieldTrialEnabled() {
+  return field_trial::FindFullName(kStrictPacingAndProbingExperimentName)
+             .empty() ||
+         field_trial::FindFullName(kScreenshareProbingBweExperimentName)
+             .empty();
+}
+
+rtc::Optional<AlrExperimentSettings>
+AlrExperimentSettings::CreateFromFieldTrial(const char* experiment_name) {
+  rtc::Optional<AlrExperimentSettings> ret;
+  std::string group_name = field_trial::FindFullName(experiment_name);
+
+  const std::string kIgnoredSuffix = "_Dogfood";
+  std::string::size_type suffix_pos = group_name.rfind(kIgnoredSuffix);
+  if (suffix_pos != std::string::npos &&
+      suffix_pos == group_name.length() - kIgnoredSuffix.length()) {
+    group_name.resize(group_name.length() - kIgnoredSuffix.length());
+  }
+
+  if (experiment_name == kScreenshareProbingBweExperimentName) {
+    // This experiment is now default-on with fixed settings.
+    // TODO(sprang): Remove this kill-switch and clean up experiment code.
+    if (group_name != "Disabled") {
+      group_name = kDefaultProbingScreenshareBweSettings;
+    }
+  }
+
+  if (group_name.empty())
+    return ret;
+
+  AlrExperimentSettings settings;
+  if (sscanf(group_name.c_str(), "%f,%" PRId64 ",%d,%d,%d,%d",
+             &settings.pacing_factor, &settings.max_paced_queue_time,
+             &settings.alr_bandwidth_usage_percent,
+             &settings.alr_start_budget_level_percent,
+             &settings.alr_stop_budget_level_percent,
+             &settings.group_id) == 6) {
+    ret.emplace(settings);
+    RTC_LOG(LS_INFO) << "Using ALR experiment settings: "
+                        "pacing factor: "
+                     << settings.pacing_factor << ", max pacer queue length: "
+                     << settings.max_paced_queue_time
+                     << ", ALR start bandwidth usage percent: "
+                     << settings.alr_bandwidth_usage_percent
+                     << ", ALR end budget level percent: "
+                     << settings.alr_start_budget_level_percent
+                     << ", ALR end budget level percent: "
+                     << settings.alr_stop_budget_level_percent
+                     << ", ALR experiment group ID: " << settings.group_id;
+  } else {
+    RTC_LOG(LS_INFO) << "Failed to parse ALR experiment: " << experiment_name;
+  }
+
+  return ret;
+}
+
+}  // namespace webrtc

rtc_base/experiments/alr_experiment.h

@@ -0,0 +1,40 @@
+/*
+ *  Copyright (c) 2018 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 RTC_BASE_EXPERIMENTS_ALR_EXPERIMENT_H_
+#define RTC_BASE_EXPERIMENTS_ALR_EXPERIMENT_H_
+
+#include "api/optional.h"
+
+namespace webrtc {
+struct AlrExperimentSettings {
+ public:
+  float pacing_factor;
+  int64_t max_paced_queue_time;
+  int alr_bandwidth_usage_percent;
+  int alr_start_budget_level_percent;
+  int alr_stop_budget_level_percent;
+  // Will be sent to the receive side for stats slicing.
+  // Can be 0..6, because it's sent as a 3 bits value and there's also
+  // reserved value to indicate absence of experiment.
+  int group_id;
+
+  static const char kScreenshareProbingBweExperimentName[];
+  static const char kStrictPacingAndProbingExperimentName[];
+  static rtc::Optional<AlrExperimentSettings> CreateFromFieldTrial(
+      const char* experiment_name);
+  static bool MaxOneFieldTrialEnabled();
+
+ private:
+  AlrExperimentSettings() = default;
+};
+}  // namespace webrtc
+
+#endif  // RTC_BASE_EXPERIMENTS_ALR_EXPERIMENT_H_