Bug 1634253 - P6. Remove MessageLoop use from gfx. r=kats,mattwoodrow

Differential Revision: https://phabricator.services.mozilla.com/D73825

gfx/layers/wr/AsyncImagePipelineManager.cpp

@@ -551,7 +551,7 @@ void AsyncImagePipelineManager::NotifyPipelinesUpdated(
 
   // Queue a runnable on the compositor thread to process the updates.
   // This will also call CheckForTextureHostsNotUsedByGPU.
-  layers::CompositorThreadHolder::Loop()->PostTask(
+  layers::CompositorThread()->Dispatch(
       NewRunnableMethod("ProcessPipelineUpdates", this,
                         &AsyncImagePipelineManager::ProcessPipelineUpdates));
 }