Remove BackForwardClient, cleanup starting a history navigation

Source/core/frame/LocalDOMWindow.cpp

Index: Source/core/frame/LocalDOMWindow.cpp
diff --git a/Source/core/frame/LocalDOMWindow.cpp b/Source/core/frame/LocalDOMWindow.cpp
index e347ad1045eab396af17f553cea46caed05003b3..8d0a331f8c7ddcd8c2baec81e6b9814f4d43eac4 100644
--- a/Source/core/frame/LocalDOMWindow.cpp
+++ b/Source/core/frame/LocalDOMWindow.cpp
@@ -83,7 +83,6 @@
 #include "core/loader/MixedContentChecker.h"
 #include "core/loader/SinkDocument.h"
 #include "core/loader/appcache/ApplicationCache.h"
-#include "core/page/BackForwardClient.h"
 #include "core/page/Chrome.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/CreateWindow.h"
@@ -986,7 +985,7 @@ void LocalDOMWindow::close(ExecutionContext* context)
     Settings* settings = m_frame->settings();
     bool allowScriptsToCloseWindows = settings && settings->allowScriptsToCloseWindows();
 
-    if (!(page->openedByDOM() || page->backForward().backForwardListCount() <= 1 || allowScriptsToCloseWindows)) {
+    if (!page->openedByDOM() && m_frame->loader().client()->backForwardLength() > 1 && !allowScriptsToCloseWindows) {
         frameConsole()->addMessage(ConsoleMessage::create(JSMessageSource, WarningMessageLevel, "Scripts may close only the windows that were opened by it."));
         return;
     }