Ignore attempts to navigate once a provisional commit has gotten too far along.

Source/core/loader/NavigationScheduler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2009 Adam Barth. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
@@ skipping 34 matching lines @@
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/loader/FrameLoaderStateMachine.h"
 #include "core/page/Page.h"
 #include "platform/SharedBuffer.h"
 #include "platform/UserGestureIndicator.h"
 #include "wtf/CurrentTime.h"
 
 namespace blink {
 
-unsigned NavigationDisablerForBeforeUnload::s_navigationDisableCount = 0;
+unsigned NavigationDisabler::s_navigationDisableCount = 0;
+
+FrameNavigationDisabler::FrameNavigationDisabler(LocalFrame* frame)
+    : m_navigationScheduler(frame->navigationScheduler())
+{
+    m_navigationScheduler.disableFrameNavigation();
+}
+
+FrameNavigationDisabler::~FrameNavigationDisabler()
+{
+    m_navigationScheduler.enableFrameNavigation();

[Nate Chapin, 2015/06/09 00:15:20]

Is it possible for NavigationScheduler to be deleted during the lifetime of
FrameNavigationDisabler?

[michaeln, 2015/06/09 01:15:02]

Not as currently used at its only callsite. It's used on the stack and there's
no way the frame can go missing prior to the stack unwinding. See
FrameLoader::commitProvisionalLoad(), the RefPtrWillBeRawPtr<LocalFrame>
protect(m_frame.get()) up top and usages of m_frame down below.

+}
 
 class ScheduledNavigation : public NoBaseWillBeGarbageCollectedFinalized<ScheduledNavigation> {
     WTF_MAKE_NONCOPYABLE(ScheduledNavigation); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(ScheduledNavigation);
 public:
     ScheduledNavigation(double delay, Document* originDocument, bool lockBackForwardList, bool isLocationChange)
         : m_delay(delay)
         , m_originDocument(originDocument)
         , m_lockBackForwardList(lockBackForwardList)
         , m_isLocationChange(isLocationChange)
         , m_wasUserGesture(UserGestureIndicator::processingUserGesture())
@@ skipping 190 matching lines @@
 {
 }
 
 bool NavigationScheduler::locationChangePending()
 {
     return m_redirect && m_redirect->isLocationChange();
 }
 
 inline bool NavigationScheduler::shouldScheduleReload() const
 {
-    return m_frame->page() && NavigationDisablerForBeforeUnload::isNavigationAllowed();
+    return m_frame->page() && isFrameNavigationAllowed() && NavigationDisabler::isNavigationAllowed();
 }
 
 inline bool NavigationScheduler::shouldScheduleNavigation(const String& url) const
 {
-    return m_frame->page() && (protocolIsJavaScript(url) || NavigationDisablerForBeforeUnload::isNavigationAllowed());
+    return m_frame->page() && isFrameNavigationAllowed() && (protocolIsJavaScript(url) || NavigationDisabler::isNavigationAllowed());
 }
 
 void NavigationScheduler::scheduleRedirect(double delay, const String& url)
 {
     if (!shouldScheduleNavigation(url))
         return;
     if (delay < 0 || delay > INT_MAX / 1000)
         return;
     if (url.isEmpty())
         return;
@@ skipping 134 matching lines @@
     m_redirect.clear();
 }
 
 DEFINE_TRACE(NavigationScheduler)
 {
     visitor->trace(m_frame);
     visitor->trace(m_redirect);
 }
 
 } // namespace blink