Disallow script execution after unload event dispatch in frame detach.

Source/core/frame/RemoteFrame.cpp

Index: Source/core/frame/RemoteFrame.cpp
diff --git a/Source/core/frame/RemoteFrame.cpp b/Source/core/frame/RemoteFrame.cpp
index 19c25da7ab56b38d49bf4dac00c1b3d263e18a8a..27be312ebff3682cef89174763131fca3c0593b2 100644
--- a/Source/core/frame/RemoteFrame.cpp
+++ b/Source/core/frame/RemoteFrame.cpp
@@ -40,6 +40,8 @@ void RemoteFrame::navigate(Document& originDocument, const KURL& url, bool lockB
 void RemoteFrame::detach()
 {
     detachChildren();
+    if (!client())

[dcheng, 2014/10/16 01:21:32]

I'm not sure if this condition is ever true at the moment, but I don't see a
reason why this might not happen in the future (the same thing that can cause
Blink to try to detach the same LocalFrame multiple times should also be able to
do the same for RemoteFrames).

+        return;
     Frame::detach();
 }