Refactor frame navigation/detach state cleanup to be more sane.

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 54881b1d527f87c67ca1461935e292a2decccbb5..0c636c0bd315c613ab58748e3a472d3563458a3d 100644
--- a/Source/core/frame/LocalDOMWindow.cpp
+++ b/Source/core/frame/LocalDOMWindow.cpp
@@ -311,15 +311,7 @@ void LocalDOMWindow::clearDocument()
     if (!m_document)
         return;
 
-    if (m_document->isActive()) {
-        // FIXME: We don't call willRemove here. Why is that OK?
-        // This detach() call is also mostly redundant. Most of the calls to
-        // this function come via DocumentLoader::createWriterFor, which
-        // always detaches the previous Document first. Only XSLTProcessor
-        // depends on this detach() call, so it seems like there's some room
-        // for cleanup.
-        m_document->detach();
-    }
+    ASSERT(!m_document->isActive());
 
     // FIXME: This should be part of ActiveDOMObject shutdown
     clearEventQueue();