Only show a beforeunload dialog if a frame has been interacted with.

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 3037 matching lines @@
   BeforeUnloadEvent* beforeUnloadEvent = BeforeUnloadEvent::create();
   beforeUnloadEvent->initEvent(EventTypeNames::beforeunload, false, true);
   m_loadEventProgress = BeforeUnloadEventInProgress;
   m_domWindow->dispatchEvent(beforeUnloadEvent, this);
   m_loadEventProgress = BeforeUnloadEventCompleted;
   if (!beforeUnloadEvent->defaultPrevented())
     defaultEventHandler(beforeUnloadEvent);
   if (!frame() || beforeUnloadEvent->returnValue().isNull())
     return true;
 
+  if (!frame()->hasReceivedUserGesture()) {
+    addConsoleMessage(ConsoleMessage::create(
+        JSMessageSource, ErrorMessageLevel,
+        "Blocked attempt to show a 'beforeunload' confirmation panel for a "
+        "frame without a user gesture."));
+    return true;
+  }
+
   if (didAllowNavigation) {
     addConsoleMessage(ConsoleMessage::create(
         JSMessageSource, ErrorMessageLevel,
         "Blocked attempt to show multiple 'beforeunload' confirmation panels "
         "for a single navigation."));
     return true;
   }
 
   String text = beforeUnloadEvent->returnValue();
   if (chromeClient.openBeforeUnloadConfirmPanel(text, m_frame, isReload)) {
@@ skipping 3573 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (blink::Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->url().getString().utf8().data());
 }
 #endif