Bug 1830820 - Introduce some delays to user input handling r=smaug

In some edge cases, we may start handling user input events that
are not supposed to be handled by the current document.

This patch introduces some delay to handle user input events.

Differential Revision: https://phabricator.services.mozilla.com/D180976

docshell/base/nsDocShell.cpp

@@ -1314,6 +1314,7 @@ void nsDocShell::FirePageHideShowNonRecursive(bool aShow) {
           mScriptGlobal ? mScriptGlobal->GetCurrentInnerWindow() : nullptr;
       if (mBrowsingContext->IsTop()) {
         doc->NotifyPossibleTitleChange(false);
+        doc->SetLoadingOrRestoredFromBFCacheTimeStampToNow();
         if (inner) {
           // Now that we have found the inner window of the page restored
           // from the history, we have to make sure that