--- a/gfx/layers/ipc/CompositorParent.cpp
+++ b/gfx/layers/ipc/CompositorParent.cpp
@@ -2394,16 +2394,21 @@ CompositorParent::UpdatePluginWindowStat
   // update the metrics to make sure they are visible again.
   if (mPluginWindowsHidden) {
     PLUGINS_LOG("[%" PRIu64 "] re-showing", aId);
     mPluginWindowsHidden = false;
     pluginMetricsChanged = true;
   }
 
   if (!lts.mPluginData.Length()) {
+    // Don't hide plugins if the previous remote layer tree didn't contain any.
+    if (!mCachedPluginData.Length()) {
+      PLUGINS_LOG("[%" PRIu64 "] nothing to hide", aId);
+      return false;
+    }
     // We will pass through here in cases where the previous shadow layer
     // tree contained visible plugins and the new tree does not. All we need
     // to do here is hide the plugins for the old tree, so don't waste time
     // calculating clipping.
     mPluginsLayerOffset = nsIntPoint(0,0);
     mPluginsLayerVisibleRegion.SetEmpty();
     uintptr_t parentWidget = (uintptr_t)lts.mParent->GetWidget();
     Unused << lts.mParent->SendHideAllPlugins(parentWidget);