Allow navigations to frames that aren't being unloaded in the unload handler.

third_party/WebKit/Source/core/loader/NavigationScheduler.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * 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 78 matching lines @@
   static bool mustReplaceCurrentItem(LocalFrame* targetFrame);
 
   Member<LocalFrame> m_frame;
   std::unique_ptr<CancellableTaskFactory> m_navigateTaskFactory;
   Member<ScheduledNavigation> m_redirect;
 
   // Exists because we can't deref m_frame in destructor.
   WebScheduler::NavigatingFrameType m_frameType;
 };
 
-class NavigationDisablerForUnload {
-  WTF_MAKE_NONCOPYABLE(NavigationDisablerForUnload);
-  STACK_ALLOCATED();
-
- public:
-  NavigationDisablerForUnload() { s_navigationDisableCount++; }
-  ~NavigationDisablerForUnload() {
-    DCHECK(s_navigationDisableCount);
-    s_navigationDisableCount--;
-  }
-  static bool isNavigationAllowed() { return !s_navigationDisableCount; }
-
- private:
-  static unsigned s_navigationDisableCount;
-};
-
 }  // namespace blink
 
 #endif  // NavigationScheduler_h