Add an extra guard to replaceDocument()

Source/bindings/core/v8/ScriptController.cpp

Index: Source/bindings/core/v8/ScriptController.cpp
diff --git a/Source/bindings/core/v8/ScriptController.cpp b/Source/bindings/core/v8/ScriptController.cpp
index 26f81df5fff5417f873c861135f85347b878354e..52e8dbc6111c155f1e4ec74338336a22dcd6fe6e 100644
--- a/Source/bindings/core/v8/ScriptController.cpp
+++ b/Source/bindings/core/v8/ScriptController.cpp
@@ -558,12 +558,7 @@ bool ScriptController::executeScriptIfJavaScriptURL(const KURL& url)
     if (!locationChangeBefore && m_frame->navigationScheduler().locationChangePending())
         return true;
 
-    // DocumentWriter::replaceDocument can cause the DocumentLoader to get deref'ed and possible destroyed,
-    // so protect it with a RefPtr.
-    if (RefPtr<DocumentLoader> loader = m_frame->document()->loader()) {
-        UseCounter::count(*m_frame->document(), UseCounter::ReplaceDocumentViaJavaScriptURL);
-        loader->replaceDocument(scriptResult, ownerDocument.get());
-    }
+    m_frame->loader().replaceDocument(scriptResult, ownerDocument.get());
     return true;
 }