Only show a beforeunload dialog if a frame has had a user gesture since its load.

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 3053 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()) {

[Charlie Reis, 2017/04/10 06:20:11]

Sanity check: Does this mean the frame has received a user gesture, or the
document?  It's confusing that it's on frame, but the documentation on
WebLocalFrame kind of implies it's about the document.

Can you add a test that beforeunload doesn't fire if there was a user gesture
for a previous document in the same frame?  (Ideally this would be a
content_browsertest that checked both same-process and cross-process, in case
there's some kind of replication that confuses us.)

[Avi (use Gerrit), 2017/05/05 15:30:04]

This is actually about the document, not the frame. It lives on the frame, is
set when the frame gets a gesture, but is reset when a new document is attached.
Done.

+    addConsoleMessage(ConsoleMessage::create(
+        JSMessageSource, ErrorMessageLevel,
+        "Blocked attempt to show a 'beforeunload' confirmation panel for a "
+        "frame that never had a user gesture since its load. "
+        "https://www.chromestatus.com/feature/5082396709879808"));
+    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 3567 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