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

Source/core/loader/NavigationScheduler.cpp

Index: Source/core/loader/NavigationScheduler.cpp
diff --git a/Source/core/loader/NavigationScheduler.cpp b/Source/core/loader/NavigationScheduler.cpp
index 2ac74b8ed38c84b0d4aca49c8d1f9eb81f40c468..adc2ecc84541d3e8cc14e6c5bb31eac0785b23ed 100644
--- a/Source/core/loader/NavigationScheduler.cpp
+++ b/Source/core/loader/NavigationScheduler.cpp
@@ -52,7 +52,18 @@
 
 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);
@@ -263,12 +274,12 @@ bool NavigationScheduler::locationChangePending()
 
 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)