From 0ae206585dc6f4218cb4dbd53be70335674d5293 Mon Sep 17 00:00:00 2001
From: Jan-Ivar Bruaroey <jib@mozilla.com>
Date: Wed, 23 Sep 2020 16:08:58 +0000
Subject: [PATCH] Bug 1654430 - Replace 200ms mainthread sleep on
 inserting/removing USB/bluetooth cam/mic/speaker with WaitFor() promise.
 r=achronop

Differential Revision: https://phabricator.services.mozilla.com/D84458
---
 dom/media/MediaManager.cpp | 40 +++++++++++++++++++++++++++++++++-----
 dom/media/MediaManager.h   |  2 ++
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/dom/media/MediaManager.cpp b/dom/media/MediaManager.cpp
index ee8da8c5e767..710b869a1b88 100644
--- a/dom/media/MediaManager.cpp
+++ b/dom/media/MediaManager.cpp
@@ -2219,14 +2219,38 @@ void MediaManager::DeviceListChanged() {
 
   // On some Windows machines, if we call EnumerateRawDevices immediately after
   // receiving devicechange event, we would get an outdated devices list.
-  PR_Sleep(PR_MillisecondsToInterval(200));
+
+  if (mDeviceChangeTimer) {
+    mDeviceChangeTimer->Cancel();
+  } else {
+    mDeviceChangeTimer = MakeRefPtr<MediaTimer>();
+  }
+  RefPtr<MediaManager> self = this;
   auto devices = MakeRefPtr<MediaDeviceSetRefCnt>();
-  EnumerateRawDevices(0, MediaSourceEnum::Camera, MediaSourceEnum::Microphone,
-                      MediaSinkEnum::Speaker, DeviceEnumerationType::Normal,
-                      DeviceEnumerationType::Normal, false, devices)
+  mDeviceChangeTimer->WaitFor(TimeDuration::FromMilliseconds(200), __func__)
       ->Then(
           GetCurrentSerialEventTarget(), __func__,
-          [self = RefPtr<MediaManager>(this), this, devices](bool) {
+          [self, this, devices] {
+            if (!MediaManager::GetIfExists()) {
+              return MgrPromise::CreateAndReject(
+                  MakeRefPtr<MediaMgrError>(MediaMgrError::Name::AbortError,
+                                            u"In shutdown"_ns),
+                  __func__);
+            }
+            return EnumerateRawDevices(
+                0, MediaSourceEnum::Camera, MediaSourceEnum::Microphone,
+                MediaSinkEnum::Speaker, DeviceEnumerationType::Normal,
+                DeviceEnumerationType::Normal, false, devices);
+          },
+          []() {
+            // Timer was canceled by us, or we're in shutdown.
+            return MgrPromise::CreateAndReject(
+                MakeRefPtr<MediaMgrError>(MediaMgrError::Name::AbortError),
+                __func__);
+          })
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [self, this, devices](bool) {
             if (!MediaManager::GetIfExists()) {
               return;
             }
@@ -3618,6 +3642,12 @@ void MediaManager::Shutdown() {
 #endif
   }
 
+  if (mDeviceChangeTimer) {
+    mDeviceChangeTimer->Cancel();
+    // Drop ref to MediaTimer early to avoid blocking SharedThreadPool shutdown
+    mDeviceChangeTimer = nullptr;
+  }
+
   {
     // Close off any remaining active windows.
 
diff --git a/dom/media/MediaManager.h b/dom/media/MediaManager.h
index ee23c67bf97e..1169288c8a87 100644
--- a/dom/media/MediaManager.h
+++ b/dom/media/MediaManager.h
@@ -41,6 +41,7 @@ class nsIPrefBranch;
 
 namespace mozilla {
 class TaskQueue;
+class MediaTimer;
 namespace dom {
 struct MediaStreamConstraints;
 struct MediaTrackConstraints;
@@ -343,6 +344,7 @@ class MediaManager final : public nsIMediaManagerService, public nsIObserver {
   nsRefPtrHashtable<nsStringHashKey, GetUserMediaTask> mActiveCallbacks;
   nsClassHashtable<nsUint64HashKey, nsTArray<nsString>> mCallIds;
   nsTArray<RefPtr<dom::GetUserMediaRequest>> mPendingGUMRequest;
+  RefPtr<MediaTimer> mDeviceChangeTimer;
   bool mCamerasMuted = false;
   bool mMicrophonesMuted = false;