Bug 1700153 - Disable SW-WR for transparent popups on early beta and the Fission experiment. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D109375

modules/libpref/init/StaticPrefList.yaml

@@ -4904,7 +4904,7 @@
 # software backend
 - name: gfx.webrender.software.unaccelerated-widget.allow
   type: RelaxedAtomicBool
-  value: @IS_EARLY_BETA_OR_EARLIER@
+  value: @IS_NIGHTLY_BUILD@
   mirror: always
 
 # Whether to force widgets that don't support acceleration to use WebRender

widget/windows/nsWindow.cpp

@@ -8554,8 +8554,7 @@ void nsWindow::PickerClosed() {
 
 bool nsWindow::WidgetTypePrefersSoftwareWebRender() const {
   return (mTransparencyMode == eTransparencyTransparent &&
-          (StaticPrefs::gfx_webrender_software_unaccelerated_widget_allow() ||
-           gfxPlatform::DoesFissionForceWebRender())) ||
+          StaticPrefs::gfx_webrender_software_unaccelerated_widget_allow()) ||
          nsBaseWidget::WidgetTypePrefersSoftwareWebRender();
 }