Bug 1804770 - add a pref to control video wakelock. r=azebrowski

Differential Revision: https://phabricator.services.mozilla.com/D165324

dom/html/HTMLVideoElement.cpp

@@ -402,15 +402,21 @@ void HTMLVideoElement::UpdateWakeLock() {
 }
 
 bool HTMLVideoElement::ShouldCreateVideoWakeLock() const {
-  // Only request wake lock for video with audio or video from media stream,
-  // because non-stream video without audio is often used as a background image.
+  if (!StaticPrefs::media_video_wakelock()) {
+    return false;
+  }
+  // Only request wake lock for video with audio or video from media
+  // stream, because non-stream video without audio is often used as a
+  // background image.
   //
-  // Some web conferencing sites route audio outside the video element, and
-  // would not be detected unless we check for media stream, so do that below.
+  // Some web conferencing sites route audio outside the video element,
+  // and would not be detected unless we check for media stream, so do
+  // that below.
   //
-  // Media streams generally aren't used as background images, though if they
-  // were we'd get false positives. If this is an issue, we could check for
-  // media stream AND document has audio playing (but that was tricky to do).
+  // Media streams generally aren't used as background images, though if
+  // they were we'd get false positives. If this is an issue, we could
+  // check for media stream AND document has audio playing (but that was
+  // tricky to do).
   return HasVideo() && (mSrcStream || HasAudio());
 }
 

modules/libpref/init/StaticPrefList.yaml

@@ -10659,6 +10659,10 @@
 #endif
   mirror: always
 
+- name: media.video-wakelock
+  type: RelaxedAtomicBool
+  value: true
+  mirror: always
 
 #---------------------------------------------------------------------------
 # Prefs starting with "midi."