--- a/dom/ipc/TabChild.cpp
+++ b/dom/ipc/TabChild.cpp
@@ -2559,30 +2559,24 @@ TabChild::InternalSetDocShellIsActive(bo
     // been a request to force paint. This is so that the BackgroundHangMonitor
     // for force painting can be made to wait again.
     if (aIsActive) {
       ProcessHangMonitor::ClearForcePaint();
     }
   });
 
   if (mCompositorOptions) {
-    // Note that |GetLayerManager()| has side-effects in that it creates a layer
-    // manager if one doesn't exist already. Calling it inside a debug-only
-    // assertion is generally bad but in this case we call it unconditionally
-    // just below so it's ok.
     MOZ_ASSERT(mPuppetWidget);
-    MOZ_ASSERT(mPuppetWidget->GetLayerManager());
-    MOZ_ASSERT(mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_CLIENT
-            || mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_WR
-            || (gfxPlatform::IsHeadless() && mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_BASIC));
+    RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+    MOZ_ASSERT(lm);
 
     // We send the current layer observer epoch to the compositor so that
     // TabParent knows whether a layer update notification corresponds to the
     // latest SetDocShellIsActive request that was made.
-    mPuppetWidget->GetLayerManager()->SetLayerObserverEpoch(mLayerObserverEpoch);
+    lm->SetLayerObserverEpoch(mLayerObserverEpoch);
   }
 
   // docshell is consider prerendered only if not active yet
   mIsPrerendered &= !aIsActive;
   nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
   if (docShell) {
     bool wasActive;
     docShell->GetIsActive(&wasActive);
@@ -3068,22 +3062,20 @@ TabChild::GetFrom(uint64_t aLayersId)
 }
 
 void
 TabChild::DidComposite(uint64_t aTransactionId,
                        const TimeStamp& aCompositeStart,
                        const TimeStamp& aCompositeEnd)
 {
   MOZ_ASSERT(mPuppetWidget);
-  MOZ_ASSERT(mPuppetWidget->GetLayerManager());
-  MOZ_ASSERT(mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_CLIENT
-             || mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_WR
-             || (gfxPlatform::IsHeadless() && mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_BASIC));
-
-  mPuppetWidget->GetLayerManager()->DidComposite(aTransactionId, aCompositeStart, aCompositeEnd);
+  RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  MOZ_ASSERT(lm);
+
+  lm->DidComposite(aTransactionId, aCompositeStart, aCompositeEnd);
 }
 
 void
 TabChild::DidRequestComposite(const TimeStamp& aCompositeReqStart,
                               const TimeStamp& aCompositeReqEnd)
 {
   nsCOMPtr<nsIDocShell> docShellComPtr = do_GetInterface(WebNavigation());
   if (!docShellComPtr) {
@@ -3106,34 +3098,29 @@ TabChild::DidRequestComposite(const Time
       MarkerTracingType::END, MarkerStackRequest::NO_STACK);
   }
 }
 
 void
 TabChild::ClearCachedResources()
 {
   MOZ_ASSERT(mPuppetWidget);
-  MOZ_ASSERT(mPuppetWidget->GetLayerManager());
-  MOZ_ASSERT(mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_CLIENT
-             || mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_WR
-             || (gfxPlatform::IsHeadless() && mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_BASIC));
-
-  mPuppetWidget->GetLayerManager()->ClearCachedResources();
+  RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  MOZ_ASSERT(lm);
+
+  lm->ClearCachedResources();
 }
 
 void
 TabChild::InvalidateLayers()
 {
   MOZ_ASSERT(mPuppetWidget);
-  MOZ_ASSERT(mPuppetWidget->GetLayerManager());
-  MOZ_ASSERT(mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_CLIENT
-             || mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_WR
-             || (gfxPlatform::IsHeadless() && mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_BASIC));
-
   RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  MOZ_ASSERT(lm);
+
   FrameLayerBuilder::InvalidateAllLayers(lm);
 }
 
 void
 TabChild::ReinitRendering()
 {
   MOZ_ASSERT(mLayersId);
 
@@ -3219,20 +3206,16 @@ TabChild::ReinitRenderingForDeviceReset(
   // Proceed with destroying and recreating the layer manager.
   ReinitRendering();
 }
 
 void
 TabChild::CompositorUpdated(const TextureFactoryIdentifier& aNewIdentifier,
                             uint64_t aDeviceResetSeqNo)
 {
-  MOZ_ASSERT(mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_CLIENT
-             || mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_WR
-             || (gfxPlatform::IsHeadless() && mPuppetWidget->GetLayerManager()->GetBackendType() == LayersBackend::LAYERS_BASIC));
-
   RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
 
   mTextureFactoryIdentifier = aNewIdentifier;
   lm->UpdateTextureFactoryIdentifier(aNewIdentifier, aDeviceResetSeqNo);
   FrameLayerBuilder::InvalidateAllLayers(lm);
 }
 
 NS_IMETHODIMP