Don't reset LoadEventProgress if frame unload has already started.

third_party/WebKit/Source/web/WebLocalFrameImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 757 matching lines @@
 {
     if (!frame())
         return true;
     return frame()->loader().shouldClose();
 }
 
 void WebLocalFrameImpl::dispatchUnloadEvent()
 {
     if (!frame())
         return;
+    SubframeLoadingDisabler disabler(frame()->document());
     frame()->loader().dispatchUnloadEvent();
 }
 
 NPObject* WebLocalFrameImpl::windowObject() const
 {
     if (!frame() || ScriptForbiddenScope::isScriptForbidden())
         return 0;
     return frame()->script().windowScriptNPObject();
 }
 
@@ skipping 1464 matching lines @@
         return WebSandboxFlags::None;
     return static_cast<WebSandboxFlags>(frame()->loader().effectiveSandboxFlags());
 }
 
 void WebLocalFrameImpl::forceSandboxFlags(WebSandboxFlags flags)
 {
     frame()->loader().forceSandboxFlags(static_cast<SandboxFlags>(flags));
 }
 
 } // namespace blink