--- a/media/webrtc/signaling/src/mediapipeline/MediaPipeline.cpp
+++ b/media/webrtc/signaling/src/mediapipeline/MediaPipeline.cpp
@@ -2143,32 +2143,30 @@ nsresult MediaPipelineReceiveAudio::Init
 void MediaPipelineReceiveAudio::SetPrincipalHandle_m(const PrincipalHandle& principal_handle)
 {
   listener_->SetPrincipalHandle_m(principal_handle);
 }
 
 class MediaPipelineReceiveVideo::PipelineListener
   : public GenericReceiveListener {
 public:
-  PipelineListener(SourceMediaStream * source, TrackID track_id)
-    : GenericReceiveListener(source, track_id),
-      width_(0),
-      height_(0),
-      image_container_(),
-      image_(),
-      monitor_("Video PipelineListener")
+  PipelineListener(SourceMediaStream* source, TrackID track_id)
+    : GenericReceiveListener(source, track_id)
+    , image_container_()
+    , image_()
+    , mutex_("Video PipelineListener")
   {
     image_container_ =
       LayerManager::CreateImageContainer(ImageContainer::ASYNCHRONOUS);
   }
 
   // Implement MediaStreamListener
   void NotifyPull(MediaStreamGraph* graph, StreamTime desired_time) override
   {
-    ReentrantMonitorAutoEnter enter(monitor_);
+    MutexAutoLock lock(mutex_);
 
     RefPtr<Image> image = image_;
     StreamTime delta = desired_time - played_ticks_;
 
     // Don't append if we've already provided a frame that supposedly
     // goes past the current aDesiredTime Doing so means a negative
     // delta and thus messes up handling of the graph
     if (delta > 0) {
@@ -2184,17 +2182,17 @@ public:
       }
     }
   }
 
   // Accessors for external writes from the renderer
   void FrameSizeChange(unsigned int width,
                        unsigned int height,
                        unsigned int number_of_streams) {
-    ReentrantMonitorAutoEnter enter(monitor_);
+    MutexAutoLock enter(mutex_);
 
     width_ = width;
     height_ = height;
   }
 
   void RenderVideoFrame(const webrtc::VideoFrameBuffer& buffer,
                         uint32_t time_stamp,
                         int64_t render_time)
@@ -2236,29 +2234,29 @@ public:
     yuvData.mPicSize = IntSize(width_, height_);
     yuvData.mStereoMode = StereoMode::MONO;
 
     if (!yuvImage->CopyData(yuvData)) {
       MOZ_ASSERT(false);
       return;
     }
 
-    ReentrantMonitorAutoEnter enter(monitor_);
+    MutexAutoLock lock(mutex_);
     image_ = yuvImage;
   }
 
 private:
   int width_;
   int height_;
   RefPtr<layers::ImageContainer> image_container_;
   RefPtr<layers::Image> image_;
-  mozilla::ReentrantMonitor monitor_; // Monitor for processing WebRTC frames.
-                                      // Protects image_ against:
-                                      // - Writing from the GIPS thread
-                                      // - Reading from the MSG thread
+  Mutex mutex_; // Mutex for processing WebRTC frames.
+                // Protects image_ against:
+                // - Writing from the GIPS thread
+                // - Reading from the MSG thread
 };
 
 class MediaPipelineReceiveVideo::PipelineRenderer : public mozilla::VideoRenderer
 {
 public:
   explicit PipelineRenderer(MediaPipelineReceiveVideo *pipeline) :
     pipeline_(pipeline) {}