Fix dynamic plugging/unplugging audio devices may not update audio input source

chromeos/audio/cras_audio_handler.cc

 // Copyright (c) 2013 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 "chromeos/audio/cras_audio_handler.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/logging.h"
 #include "base/sys_info.h"
+#include "base/system_monitor/system_monitor.h"
 #include "chromeos/audio/audio_devices_pref_handler_stub.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 
 using std::max;
 using std::min;
 
 namespace chromeos {
 
 namespace {
 
@@ skipping 1208 matching lines @@
   if (!active_device || !active_device->active)
     active_node_id = 0;
 
   if (!active_node_id || hotplug_nodes.empty() || hotplug_nodes.size() > 1) {
     HandleNonHotplugNodesChange(is_input, hotplug_nodes, has_device_change,
                                 has_device_removed, active_device_removed);
   } else {
     // Typical user hotplug case.
     HandleHotPlugDevice(hotplug_nodes.top(), devices_pq);
   }
+
+  // content::MediaStreamManager listens to
+  // base::SystemMonitor::DevicesChangedObserver for audio capture devices,
+  // and updates EnumerateDevices when OnDevicesChanged is called.
+  if (is_input) {
+    base::SystemMonitor* monitor = base::SystemMonitor::Get();
+    // In some unittest, |monitor| might be nullptr.
+    if (!monitor)
+      return;
+    monitor->ProcessDevicesChanged(
+        base::SystemMonitor::DeviceType::DEVTYPE_AUDIO_CAPTURE);
+  }
 }
 
 void CrasAudioHandler::HandleGetNodes(const chromeos::AudioNodeList& node_list,
                                       bool success) {
   if (!success) {
     LOG_IF(ERROR, log_errors_) << "Failed to retrieve audio nodes data";
     return;
   }
 
   UpdateDevicesAndSwitchActive(node_list);
@@ skipping 91 matching lines @@
                      hdmi_rediscover_grace_period_duration_in_ms_),
       this, &CrasAudioHandler::UpdateAudioAfterHDMIRediscoverGracePeriod);
 }
 
 void CrasAudioHandler::SetHDMIRediscoverGracePeriodForTesting(
     int duration_in_ms) {
   hdmi_rediscover_grace_period_duration_in_ms_ = duration_in_ms;
 }
 
 }  // namespace chromeos