Bug 1479939 - Ensure we tell WR to remove the compositable pipelines when clearing resources. r=sotaro

MozReview-Commit-ID: AxuvERUalhb

--HG--
extra : rebase_source : 674a20346c234912f7389d9fc7078c956cf08fc7

gfx/layers/wr/WebRenderBridgeParent.cpp

@@ -1710,6 +1710,7 @@ WebRenderBridgeParent::ClearResources()
     RefPtr<WebRenderImageHost> host = entry.second;
     host->ClearWrBridge();
     mAsyncImageManager->RemoveAsyncImagePipeline(pipelineId, txn);
+    txn.RemovePipeline(pipelineId);
   }
   mAsyncCompositables.clear();
   for (const auto& entry : mSharedSurfaceIds) {