Bug 1821629 [Pipewire/DMABuf] Don't create dmabuf backend if it's disabled r=ng,webrtc-reviewers

Depends on D172224

Differential Revision: https://phabricator.services.mozilla.com/D172229

third_party/libwebrtc/modules/desktop_capture/linux/wayland/shared_screencast_stream.cc

@@ -419,7 +419,9 @@ bool SharedScreenCastStreamPrivate::StartScreenCastStream(
     RTC_LOG(LS_ERROR) << "Unable to open PipeWire library";
     return false;
   }
-  egl_dmabuf_ = std::make_unique<EglDmaBuf>();
+  if (mozilla::gfx::IsDMABufEnabled()) {
+    egl_dmabuf_ = std::make_unique<EglDmaBuf>();
+  }
 
   pw_stream_node_id_ = stream_node_id;
 
@@ -508,7 +510,8 @@ bool SharedScreenCastStreamPrivate::StartScreenCastStream(
     for (uint32_t format : {SPA_VIDEO_FORMAT_BGRA, SPA_VIDEO_FORMAT_RGBA,
                             SPA_VIDEO_FORMAT_BGRx, SPA_VIDEO_FORMAT_RGBx}) {
       // Modifiers can be used with PipeWire >= 0.3.33
-      if (has_required_pw_client_version && has_required_pw_server_version) {
+      if (egl_dmabuf_ &&
+          has_required_pw_client_version && has_required_pw_server_version) {
         modifiers_ = egl_dmabuf_->QueryDmaBufModifiers(format);
 
         if (!modifiers_.empty()) {
@@ -927,7 +930,7 @@ bool SharedScreenCastStreamPrivate::ProcessDMABuffer(
 
   const uint n_planes = spa_buffer->n_datas;
 
-  if (!n_planes) {
+  if (!n_planes || !egl_dmabuf_) {
     return false;
   }