Detach old frame on 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 4f95ddfb6d8fea37c74c90f1e9df0369f3e741f3..482762aa50032fbff9c3d9e9f9cc9cea87865858 100644
--- a/Source/core/frame/Frame.cpp
+++ b/Source/core/frame/Frame.cpp
@@ -149,14 +149,15 @@ ChromeClient& Frame::chromeClient() const
     return emptyChromeClient();
 }
 
-void Frame::finishSwapFrom(Frame* old)
+void Frame::prepareSwapFrom(Frame* old)
 {
     WindowProxyManager* oldManager = old->windowProxyManager();
-    // FIXME: In the future, the Blink API layer will be calling detach() on the
-    // old frame prior to completing the swap. However, detach calls
-    // clearForClose() instead of clearForNavigation(). Make sure this doesn't
-    // become a no-op when that lands, since it's important to detach the global.
     oldManager->clearForNavigation();
+}
+
+void Frame::finishSwapFrom(Frame* old)
+{
+    WindowProxyManager* oldManager = old->windowProxyManager();
     windowProxyManager()->takeGlobalFrom(oldManager);
 }