Add field trial for vp8 cpu speed configuration for arm.

Bug: none
Change-Id: I90c2475a229a1f10016e2ad84029e19b5a4f9966
Reviewed-on: https://webrtc-review.googlesource.com/c/107340
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25484}

rtc_base/experiments/cpu_speed_experiment.cc

@@ -0,0 +1,70 @@
+/*
+ *  Copyright 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/cpu_speed_experiment.h"
+
+#include <string>
+
+#include "rtc_base/logging.h"
+#include "system_wrappers/include/field_trial.h"
+
+namespace webrtc {
+namespace {
+constexpr char kFieldTrial[] = "WebRTC-VP8-CpuSpeed-Arm";
+constexpr int kMinSetting = -16;
+constexpr int kMaxSetting = -1;
+}  // namespace
+
+absl::optional<std::vector<CpuSpeedExperiment::Config>>
+CpuSpeedExperiment::GetConfigs() {
+  if (!webrtc::field_trial::IsEnabled(kFieldTrial))
+    return absl::nullopt;
+
+  const std::string group = webrtc::field_trial::FindFullName(kFieldTrial);
+  if (group.empty())
+    return absl::nullopt;
+
+  std::vector<Config> configs(3);
+  if (sscanf(group.c_str(), "Enabled-%d,%d,%d,%d,%d,%d", &(configs[0].pixels),
+             &(configs[0].cpu_speed), &(configs[1].pixels),
+             &(configs[1].cpu_speed), &(configs[2].pixels),
+             &(configs[2].cpu_speed)) != 6) {
+    RTC_LOG(LS_WARNING) << "Too few parameters provided.";
+    return absl::nullopt;
+  }
+
+  for (const auto& config : configs) {
+    if (config.cpu_speed < kMinSetting || config.cpu_speed > kMaxSetting) {
+      RTC_LOG(LS_WARNING) << "Unsupported cpu speed setting, value ignored.";
+      return absl::nullopt;
+    }
+  }
+
+  for (size_t i = 1; i < configs.size(); ++i) {
+    if (configs[i].pixels < configs[i - 1].pixels ||
+        configs[i].cpu_speed > configs[i - 1].cpu_speed) {
+      RTC_LOG(LS_WARNING) << "Invalid parameter value provided.";
+      return absl::nullopt;
+    }
+  }
+
+  return absl::optional<std::vector<Config>>(configs);
+}
+
+int CpuSpeedExperiment::GetValue(int pixels,
+                                 const std::vector<Config>& configs) {
+  for (const auto& config : configs) {
+    if (pixels <= config.pixels)
+      return config.cpu_speed;
+  }
+  return kMinSetting;
+}
+
+}  // namespace webrtc