Simplify WindowProxy handoff in WebFrame::swap().

Source/core/frame/Frame.cpp

Index: Source/core/frame/Frame.cpp
diff --git a/Source/core/frame/Frame.cpp b/Source/core/frame/Frame.cpp
index 58e7d90971df8449c3d2bdc69ce2da5e12fe01c1..127d4ac26f229b0d97a73ef2a34aa5cec3f4dc15 100644
--- a/Source/core/frame/Frame.cpp
+++ b/Source/core/frame/Frame.cpp
@@ -158,15 +158,10 @@ ChromeClient& Frame::chromeClient() const
     return emptyChromeClient();
 }
 
-void Frame::prepareSwapFrom(Frame* old)
-{
-    WindowProxyManager* oldManager = old->windowProxyManager();
-    oldManager->clearForNavigation();
-}
-
 void Frame::finishSwapFrom(Frame* old)
 {
     WindowProxyManager* oldManager = old->windowProxyManager();
+    oldManager->clearForNavigation();
     windowProxyManager()->takeGlobalFrom(oldManager);
 }