Remove device enumeration, caching and monitoring from MediaStreamManager.

content/browser/renderer_host/media/media_devices_manager.cc

+// Copyright 2016 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.
+
+#include "content/browser/renderer_host/media/media_devices_manager.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <algorithm>
+#include <string>
+
+#include "base/command_line.h"
+#include "base/location.h"
+#include "base/strings/stringprintf.h"
+#include "base/task_runner_util.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "build/build_config.h"
+#include "content/browser/renderer_host/media/media_stream_manager.h"
+#include "content/browser/renderer_host/media/video_capture_manager.h"
+#include "content/public/browser/browser_thread.h"
+#include "media/audio/audio_device_description.h"
+#include "media/audio/audio_manager.h"
+#include "media/base/media_switches.h"
+
+#if defined(OS_MACOSX)
+#include "base/bind_helpers.h"
+#include "base/profiler/scoped_tracker.h"
+#include "base/single_thread_task_runner.h"
+#include "content/browser/browser_main_loop.h"
+#include "media/device_monitors/device_monitor_mac.h"
+#endif
+
+namespace content {
+
+namespace {
+
+// Private helper method to generate a string for the log message that lists the
+// human readable names of |devices|.
+std::string GetLogMessageString(MediaDeviceType device_type,
+                                const MediaDeviceInfoArray& device_infos) {
+  std::string output_string =
+      base::StringPrintf("Getting devices for stream type %d:\n", device_type);
+  if (device_infos.empty())
+    return output_string + "No devices found.";
+  for (const auto& device_info : device_infos)
+    output_string += "  " + device_info.label + "\n";
+  return output_string;
+}
+
+MediaDeviceInfoArray EnumerateAudioDevicesOnDeviceThread(
+    media::AudioManager* audio_manager,
+    bool is_input) {
+  DCHECK(audio_manager->GetTaskRunner()->BelongsToCurrentThread());
+
+  MediaDeviceInfoArray snapshot;
+  media::AudioDeviceNames device_names;
+  if (is_input)
+    audio_manager->GetAudioInputDeviceNames(&device_names);
+  else
+    audio_manager->GetAudioOutputDeviceNames(&device_names);
+
+  for (const media::AudioDeviceName& name : device_names) {
+    snapshot.emplace_back(
+        name.unique_id, name.device_name,
+        is_input ? audio_manager->GetGroupIDInput(name.unique_id)
+                 : audio_manager->GetGroupIDOutput(name.unique_id));
+  }
+
+  return snapshot;
+}
+
+MediaDeviceInfoArray GetFakeAudioDevices(bool is_input) {
+  MediaDeviceInfoArray result;
+  if (is_input) {
+    result.emplace_back(media::AudioDeviceDescription::kDefaultDeviceId,
+                        "Fake Default Audio Input",
+                        "fake_group_audio_input_default");
+    result.emplace_back("fake_audio_input_1", "Fake Audio Input 1",
+                        "fake_group_audio_input_1");
+    result.emplace_back("fake_audio_input_2", "Fake Audio Input 2",
+                        "fake_group_audio_input_2");
+  } else {
+    result.emplace_back(media::AudioDeviceDescription::kDefaultDeviceId,
+                        "Fake Default Audio Output",
+                        "fake_group_audio_output_default");
+    result.emplace_back("fake_audio_output_1", "Fake Audio Output 1",
+                        "fake_group_audio_output_1");
+    result.emplace_back("fake_audio_output_2", "Fake Audio Output 2",
+                        "fake_group_audio_output_2");
+  }
+
+  return result;
+}
+
+}  // namespace
+
+struct MediaDevicesManager::EnumerationRequest {
+  EnumerationRequest(const BoolDeviceTypes& requested_types,
+                     const EnumerationCallback& callback)
+      : callback(callback) {
+    requested = requested_types;
+    has_seen_result.fill(false);
+  }
+
+  BoolDeviceTypes requested;
+  BoolDeviceTypes has_seen_result;
+  EnumerationCallback callback;
+};
+
+// This class helps manage the consistency of cached enumeration results.
+// It uses a sequence number for each invalidation and enumeration.
+// A cache is considered valid if the sequence number for the last enumeration
+// is greater than the sequence number for the last invalidation.
+// The advantage of using invalidations over directly issuing enumerations upon
+// each system notification is that some platforms issue multiple notifications
+// on each device change. The cost of performing multiple invalidations is
+// significantly lower than the cost of issuing multiple unnecessary
+// enumerations.
+class MediaDevicesManager::CacheInfo {
+ public:
+  CacheInfo()
+      : current_event_sequence_(0),
+        seq_last_update_(0),
+        seq_last_invalidation_(0),
+        is_update_ongoing_(false) {}
+
+  void InvalidateCache() { seq_last_invalidation_ = NewEventSequence(); }
+
+  bool IsLastUpdateValid() {
+    return seq_last_update_ > seq_last_invalidation_ && !is_update_ongoing_;
+  }
+
+  void UpdateStarted() {
+    DCHECK(!is_update_ongoing_);
+    seq_last_update_ = NewEventSequence();
+    is_update_ongoing_ = true;
+  }
+
+  void UpdateCompleted() {
+    DCHECK(is_update_ongoing_);
+    is_update_ongoing_ = false;
+  }
+
+  bool is_update_ongoing() { return is_update_ongoing_; }
+
+ private:
+  int64_t NewEventSequence() { return ++current_event_sequence_; }
+
+  int64_t current_event_sequence_;
+  int64_t seq_last_update_;
+  int64_t seq_last_invalidation_;
+  bool is_update_ongoing_;
+};
+
+MediaDevicesManager::MediaDevicesManager(
+    media::AudioManager* audio_manager,
+    const scoped_refptr<VideoCaptureManager>& video_capture_manager,
+    MediaStreamManager* media_stream_manager)
+    : use_fake_devices_(base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kUseFakeDeviceForMediaStream)),
+      audio_manager_(audio_manager),
+      video_capture_manager_(video_capture_manager),
+      media_stream_manager_(media_stream_manager),
+      cache_infos_(NUM_MEDIA_DEVICE_TYPES),
+      monitoring_started_(false),
+      weak_factory_(this) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(audio_manager_);
+  DCHECK(video_capture_manager_.get());
+  cache_policies_.fill(CachePolicy::NO_CACHE);
+  has_seen_result_.fill(false);
+}
+
+MediaDevicesManager::~MediaDevicesManager() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+}
+
+void MediaDevicesManager::EnumerateDevices(
+    const BoolDeviceTypes& requested_types,
+    const EnumerationCallback& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  StartMonitoring();
+
+  requests_.emplace_back(requested_types, callback);
+  bool all_results_cached = true;
+  for (size_t i = 0; i < NUM_MEDIA_DEVICE_TYPES; ++i) {
+    if (requested_types[i] && cache_policies_[i] == CachePolicy::NO_CACHE) {
+      all_results_cached = false;
+      DoEnumerateDevices(static_cast<MediaDeviceType>(i));
+    }
+  }
+
+  if (all_results_cached)
+    ProcessRequests();
+}
+
+void MediaDevicesManager::SetCachePolicy(MediaDeviceType type,
+                                         CachePolicy policy) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(IsValidMediaDeviceType(type));
+  if (cache_policies_[type] == policy)
+    return;
+
+  cache_policies_[type] = policy;
+  // If the new policy is SYSTEM_MONITOR, issue an enumeration to populate the
+  // cache.
+  if (policy == CachePolicy::SYSTEM_MONITOR) {
+    cache_infos_[type].InvalidateCache();
+    DoEnumerateDevices(type);

[hta - Chromium, 2016/09/20 10:55:29]

If OS_MACOSX and type = MEDIA_DEVICE_TYPE_OUTPUT, should this fail?

[Guido Urdaneta, 2016/09/20 13:59:27]

This just changes the policy, so there is no failure there.
If it's Mac, the policy is set to NO_CACHE for audio output in
StartMonitoring().
Since SetCachePolicy is now private, this can no longer be accidentally misused.

+  }
+}
+
+void MediaDevicesManager::StartMonitoring() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (monitoring_started_)
+    return;
+
+  if (!base::SystemMonitor::Get())
+    return;
+
+  monitoring_started_ = true;
+  base::SystemMonitor::Get()->AddDevicesChangedObserver(this);
+
+  for (size_t i = 0; i < NUM_MEDIA_DEVICE_TYPES; ++i) {
+    DCHECK(cache_policies_[i] != CachePolicy::SYSTEM_MONITOR);
+    SetCachePolicy(static_cast<MediaDeviceType>(i),
+                   CachePolicy::SYSTEM_MONITOR);
+  }
+
+#if defined(OS_MACOSX)
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&MediaDevicesManager::StartMonitoringOnUIThread,
+                 base::Unretained(this)));
+
+  // TODO(guidou): Remove this statement once the Mac device monitor is fixed to
+  //  correctly report device-change events for output-only audio devices.
+  // See http://crbug.com/648173.
+  SetCachePolicy(MEDIA_DEVICE_TYPE_AUDIO_OUTPUT, CachePolicy::NO_CACHE);
+#endif
+}
+
+#if defined(OS_MACOSX)
+void MediaDevicesManager::StartMonitoringOnUIThread() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  // TODO(erikchen): Remove ScopedTracker below once crbug.com/458404 is fixed.

[hta - Chromium, 2016/09/20 10:55:29]

Is this code copied from elsewhere, including TODOs?
Is there a possibility of reusing that implementation rather than recoding it
here?

[Guido Urdaneta, 2016/09/20 13:59:27]

This is code removed from MediaStreamManager.
It is practically unmodified so that it behaves exactly the same.

+  tracked_objects::ScopedTracker tracking_profile1(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "458404 MediaDevicesManager::GetBrowserMainLoop"));
+  BrowserMainLoop* browser_main_loop = content::BrowserMainLoop::GetInstance();
+  if (!browser_main_loop)
+    return;
+
+  // TODO(erikchen): Remove ScopedTracker below once crbug.com/458404 is
+  // fixed.
+  tracked_objects::ScopedTracker tracking_profile2(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "458404 MediaDevicesManager::GetTaskRunner"));
+  const scoped_refptr<base::SingleThreadTaskRunner> task_runner =
+      audio_manager_->GetTaskRunner();
+  // TODO(erikchen): Remove ScopedTracker below once crbug.com/458404 is
+  // fixed.
+  tracked_objects::ScopedTracker tracking_profile3(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "458404 MediaDevicesManager::DeviceMonitorMac::StartMonitoring"));
+  browser_main_loop->device_monitor_mac()->StartMonitoring(task_runner);
+}
+#endif
+
+void MediaDevicesManager::StopMonitoring() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (!monitoring_started_)
+    return;
+  base::SystemMonitor::Get()->RemoveDevicesChangedObserver(this);
+  monitoring_started_ = false;
+  for (size_t i = 0; i < NUM_MEDIA_DEVICE_TYPES; ++i)
+    SetCachePolicy(static_cast<MediaDeviceType>(i), CachePolicy::NO_CACHE);
+}
+
+bool MediaDevicesManager::IsMonitoringStarted() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  return monitoring_started_;
+}
+
+void MediaDevicesManager::OnDevicesChanged(
+    base::SystemMonitor::DeviceType device_type) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  switch (device_type) {
+    case base::SystemMonitor::DEVTYPE_AUDIO:
+      HandleDevicesChanged(MEDIA_DEVICE_TYPE_AUDIO_INPUT);
+      HandleDevicesChanged(MEDIA_DEVICE_TYPE_AUDIO_OUTPUT);
+      break;
+    case base::SystemMonitor::DEVTYPE_VIDEO_CAPTURE:
+      HandleDevicesChanged(MEDIA_DEVICE_TYPE_VIDEO_INPUT);
+      break;
+    default:
+      break;  // Uninteresting device change.
+  }
+}
+
+MediaDeviceInfoArray MediaDevicesManager::GetCachedDeviceInfo(
+    MediaDeviceType type) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  return current_snapshot_[type];
+}
+
+void MediaDevicesManager::DoEnumerateDevices(MediaDeviceType type) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(IsValidMediaDeviceType(type));
+  CacheInfo& cache_info = cache_infos_[type];
+  if (cache_info.is_update_ongoing())
+    return;
+
+  cache_info.UpdateStarted();
+  switch (type) {
+    case MEDIA_DEVICE_TYPE_AUDIO_INPUT:
+      EnumerateAudioDevices(true /* is_input */);
+      break;
+    case MEDIA_DEVICE_TYPE_VIDEO_INPUT:
+      video_capture_manager_->EnumerateDevices(
+          base::Bind(&MediaDevicesManager::VideoInputDevicesEnumerated,
+                     weak_factory_.GetWeakPtr()));
+      break;
+    case MEDIA_DEVICE_TYPE_AUDIO_OUTPUT:
+      EnumerateAudioDevices(false /* is_input */);
+      break;
+    default:
+      NOTREACHED();
+  }
+}
+
+void MediaDevicesManager::EnumerateAudioDevices(bool is_input) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  MediaDeviceType type =
+      is_input ? MEDIA_DEVICE_TYPE_AUDIO_INPUT : MEDIA_DEVICE_TYPE_AUDIO_OUTPUT;
+  if (use_fake_devices_) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(&MediaDevicesManager::DevicesEnumerated,
+                              weak_factory_.GetWeakPtr(), type,
+                              GetFakeAudioDevices(is_input)));
+    return;
+  }
+  base::PostTaskAndReplyWithResult(
+      audio_manager_->GetTaskRunner(), FROM_HERE,
+      base::Bind(&EnumerateAudioDevicesOnDeviceThread, audio_manager_,
+                 is_input),
+      base::Bind(&MediaDevicesManager::DevicesEnumerated,
+                 weak_factory_.GetWeakPtr(), type));
+}
+
+void MediaDevicesManager::VideoInputDevicesEnumerated(
+    const media::VideoCaptureDeviceDescriptors& descriptors) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  MediaDeviceInfoArray snapshot;
+  for (const auto& descriptor : descriptors) {
+    snapshot.emplace_back(descriptor.device_id, descriptor.GetNameAndModel(),
+                          std::string());
+  }
+  DevicesEnumerated(MEDIA_DEVICE_TYPE_VIDEO_INPUT, snapshot);
+}
+
+void MediaDevicesManager::DevicesEnumerated(
+    MediaDeviceType type,
+    const MediaDeviceInfoArray& snapshot) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(IsValidMediaDeviceType(type));
+  UpdateSnapshot(type, snapshot);
+  cache_infos_[type].UpdateCompleted();
+  has_seen_result_[type] = true;
+
+  std::string log_message =
+      "New device enumeration result:\n" + GetLogMessageString(type, snapshot);
+  MediaStreamManager::SendMessageToNativeLog(log_message);
+
+  if (cache_policies_[type] == CachePolicy::NO_CACHE) {
+    for (auto& request : requests_)
+      request.has_seen_result[type] = true;
+  }
+
+  // Note that IsLastUpdateValid is always true when policy is NO_CACHE.
+  if (cache_infos_[type].IsLastUpdateValid()) {
+    ProcessRequests();
+  } else {
+    DoEnumerateDevices(type);
+  }
+}
+
+void MediaDevicesManager::UpdateSnapshot(
+    MediaDeviceType type,
+    const MediaDeviceInfoArray& new_snapshot) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(IsValidMediaDeviceType(type));
+
+  // Only cache the device list when the device list has been changed.
+  bool need_update_device_change_subscribers = false;
+  MediaDeviceInfoArray& old_snapshot = current_snapshot_[type];
+
+  if (old_snapshot.size() != new_snapshot.size() ||
+      !std::equal(new_snapshot.begin(), new_snapshot.end(),
+                  old_snapshot.begin())) {
+    if (type == MEDIA_DEVICE_TYPE_AUDIO_INPUT ||
+        type == MEDIA_DEVICE_TYPE_VIDEO_INPUT) {
+      NotifyMediaStreamManager(type, new_snapshot);
+    }
+
+    // Do not notify device-change subscribers after the first enumeration
+    // result, since it is not due to an actual device change.
+    need_update_device_change_subscribers =
+        has_seen_result_[type] &&
+        (old_snapshot.size() != 0 || new_snapshot.size() != 0);
+    current_snapshot_[type] = new_snapshot;
+  }
+
+  if (need_update_device_change_subscribers)
+    NotifyDeviceChangeSubscribers(type, new_snapshot);
+}
+
+void MediaDevicesManager::ProcessRequests() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  requests_.erase(std::remove_if(requests_.begin(), requests_.end(),

[hta - Chromium, 2016/09/20 10:55:29]

I'm confused by this construct. It seems to me that we first remove all the
ready requests from requests_ by remove_if, and then erase the remaining
members. But remove_if is supposed to return a value pointing past the end, so
request_.erase() should then be called on (equivalent) (request_.end(),
request_.end()), which erases nothing. Are you sure we have test coverage for
all the combinations of ready and non-ready requests?

std::remove_if is a C++ 17 feature according to
http://en.cppreference.com/w/cpp/algorithm/remove - is it approved for use in
Chromium?

[Guido Urdaneta, 2016/09/20 13:59:27]

This version of remove_if is from C++98.
It is indeed a confusing construct, but it is the way one is supposed to remove
elements from an STL collection while iterating it.
It's so peculiar that it has its own Wikipedia page :-) 
https://en.wikipedia.org/wiki/Erase%E2%80%93remove_idiom

+                                 [this](const EnumerationRequest& request) {
+                                   if (IsEnumerationRequestReady(request)) {
+                                     request.callback.Run(current_snapshot_);
+                                     return true;
+                                   }
+                                   return false;
+                                 }),
+                  requests_.end());
+}
+
+bool MediaDevicesManager::IsEnumerationRequestReady(
+    const EnumerationRequest& request_info) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  bool is_ready = true;
+  for (size_t i = 0; i < NUM_MEDIA_DEVICE_TYPES; ++i) {
+    if (!request_info.requested[i])
+      continue;
+    switch (cache_policies_[i]) {
+      case CachePolicy::SYSTEM_MONITOR:
+        if (!cache_infos_[i].IsLastUpdateValid())
+          is_ready = false;
+        break;
+      case CachePolicy::NO_CACHE:
+        if (!request_info.has_seen_result[i])
+          is_ready = false;
+        break;
+      default:
+        NOTREACHED();
+    }
+  }
+  return is_ready;
+}
+
+void MediaDevicesManager::HandleDevicesChanged(MediaDeviceType type) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(IsValidMediaDeviceType(type));
+  cache_infos_[type].InvalidateCache();
+  DoEnumerateDevices(type);
+}
+
+void MediaDevicesManager::NotifyMediaStreamManager(
+    MediaDeviceType type,
+    const MediaDeviceInfoArray& new_snapshot) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(IsValidMediaDeviceType(type));
+  DCHECK(type == MEDIA_DEVICE_TYPE_AUDIO_INPUT ||
+         type == MEDIA_DEVICE_TYPE_VIDEO_INPUT);
+  MediaDeviceInfoArray& old_snapshot = current_snapshot_[type];
+

[hta - Chromium, 2016/09/20 10:55:29]

Why isn't the "if media_stream_manager_" test up here with a "return"?

Is the function doing anything but notifying the media stream manager?

[Guido Urdaneta, 2016/09/20 13:59:27]

Done.

+  for (const auto& old_device_info : old_snapshot) {
+    auto it = std::find_if(new_snapshot.begin(), new_snapshot.end(),
+                           [&old_device_info](const MediaDeviceInfo& info) {
+                             return info.device_id == old_device_info.device_id;
+                           });
+
+    // If a device was removed, notify the MediaStreamManager to stop all
+    // streams using that device.
+    if (it == new_snapshot.end() && media_stream_manager_)
+      media_stream_manager_->StopRemovedDevice(type, old_device_info);
+  }
+
+  if (media_stream_manager_)
+    media_stream_manager_->NotifyDevicesChanged(type, new_snapshot);
+}
+
+void MediaDevicesManager::NotifyDeviceChangeSubscribers(
+    MediaDeviceType type,
+    const MediaDeviceInfoArray& snapshot) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  // TODO(guidou): Use device types instead of stream types, and remove the
+  // call to MediaStreamManager once handling of device-change subscriptions
+  // is removed from MediaStreamManager. See http://crbug.com/334244.
+  MediaStreamType stream_type = type == MEDIA_DEVICE_TYPE_VIDEO_INPUT
+                                    ? MEDIA_DEVICE_VIDEO_CAPTURE
+                                    : MEDIA_DEVICE_AUDIO_CAPTURE;

[hta - Chromium, 2016/09/20 10:55:29]

This will return MEDIA_DEVICE_AUDIO_CAPTURE for MEDIA_DEVICE_TYPE_AUDIO_OUTPUT.
Suggest that you DCHECK that the argument is either
MEDIA_DEVICE_TYPE_VIDEO_INPUT or MEDIA_DEVICE_TYPE_AUDIO_INPUT before doing this
switch.

Or even more explicit:

switch(type) {
  case MEDIA_DEVICE_TYPE_VIDEO_INPUT:
     ....
  case MEDIA_DEVICE_TYPE_AUDIO_INPUT:
     ....
  default:
     NOTREACHED()
}

 

[Guido Urdaneta, 2016/09/20 13:59:27]

Unfortunately, it is that way because there is no separate permission for audio
output devices yet.
Added a comment explaining the situation and renamed the variable to
|permission_type| to make it clearer.
Did add a DCHECK to make sure it's a valid device type.

+  if (media_stream_manager_)
+    media_stream_manager_->NotifyDeviceChangeSubscribers(stream_type);
+}
+
+}  // namespace content