text: // Copyright (c) 2020 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_THERMAL_RESOURCE_H_
  #define THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_THERMAL_RESOURCE_H_
  
  #include "base/feature_list.h"
  #include "base/memory/scoped_refptr.h"
  #include "base/single_thread_task_runner.h"
  #include "base/synchronization/lock.h"
  #include "base/thread_annotations.h"
  #include "third_party/blink/public/mojom/peerconnection/peer_connection_tracker.mojom-blink.h"
  #include "third_party/blink/renderer/modules/modules_export.h"
  #include "third_party/webrtc/api/adaptation/resource.h"
  
  namespace blink {
  
  MODULES_EXPORT extern const base::Feature kWebRtcThermalResource;
  
  // The ThermalResource reports kOveruse or kUnderuse every 10 seconds(*) while
  // it has a registered listener and the DeviceThermalMeasurement is known.
  // Because OnThermalMeasurement() only happens when the thermal state changes,
  // repeated kOveruse is needed to adapt multiple steps.
  //
  // Based on [1] and manual observations, we do not want to adapt if thermals are
  // kNominal or kFair so we map these to kUnderuse. But if thermals are kSerious
  // or kCritical this is a strong signal from the OS that "corrective action" or
  // "immediate corrective action" is needed.
  //
  // (*) It can easily take a minute before the thermal state changes after load
  // distribution has changed, so the effects of ThermalResource is likely to
  // result in either maximally adapted or not adapted at all. The repeated
  // interval of 10 seconds was somewhat arbitrarily chosen but was chosen as a
  // tradeoff between giving the OS time to measure the new load and not making
  // the resource too spammy.
  //
  // [1]
  // https://developer.apple.com/library/archive/documentation/Performance/Conceptual/power_efficiency_guidelines_osx/RespondToThermalStateChanges.html
  class MODULES_EXPORT ThermalResource : public webrtc::Resource {
   public:
    static scoped_refptr<ThermalResource> Create(
        scoped_refptr<base::SequencedTaskRunner> task_runner);
  
    explicit ThermalResource(
        scoped_refptr<base::SequencedTaskRunner> task_runner);
    ~ThermalResource() override = default;
  
    void OnThermalMeasurement(mojom::blink::DeviceThermalState measurement);
  
    // webrtc::Resource implementation.
    std::string Name() const override;
    void SetResourceListener(webrtc::ResourceListener* listener) override;
  
   private:
    void ReportMeasurement(size_t measurement_id);
    void ReportMeasurementWhileHoldingLock(size_t measurement_id)
        EXCLUSIVE_LOCKS_REQUIRED(&lock_);
  
    const scoped_refptr<base::SequencedTaskRunner> task_runner_;
    base::Lock lock_;
    webrtc::ResourceListener* listener_ GUARDED_BY(&lock_) = nullptr;
    mojom::blink::DeviceThermalState measurement_ GUARDED_BY(&lock_) =
        mojom::blink::DeviceThermalState::kUnknown;
    size_t measurement_id_ GUARDED_BY(&lock_) = 0u;
  };
  
  }  // namespace blink
  
  #endif  // THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_THERMAL_RESOURCE_H_
  