Make RendererGpuVideoDecoderFactories live on arbitrary threads.

content/renderer/media/webmediaplayer_impl.cc

Index: content/renderer/media/webmediaplayer_impl.cc
diff --git a/content/renderer/media/webmediaplayer_impl.cc b/content/renderer/media/webmediaplayer_impl.cc
index 32f228f86d2a37a31992c2857eade733c3e7478e..bffda93d2c1b4b9c503e549f0aa7265496c4a53c 100644
--- a/content/renderer/media/webmediaplayer_impl.cc
+++ b/content/renderer/media/webmediaplayer_impl.cc
@@ -1100,10 +1100,8 @@ void WebMediaPlayerImpl::StartPipeline(WebKit::WebMediaSource* media_source) {
   // Create our video decoders and renderer.
   ScopedVector<media::VideoDecoder> video_decoders;
 
-  if (gpu_factories_.get()) {
-    video_decoders.push_back(new media::GpuVideoDecoder(
-        media_loop_, gpu_factories_));
-  }
+  if (gpu_factories_.get())
+    video_decoders.push_back(new media::GpuVideoDecoder(gpu_factories_));
 
   // TODO(phajdan.jr): Remove ifdefs when libvpx with vp9 support is released
   // (http://crbug.com/174287) .