Disallow adding ContextLifecycleObservers during iteration.

Source/core/frame/FrameDestructionObserver.cpp

Index: Source/core/frame/FrameDestructionObserver.cpp
diff --git a/Source/core/frame/FrameDestructionObserver.cpp b/Source/core/frame/FrameDestructionObserver.cpp
deleted file mode 100644
index 2d6c71521994a24c810d81acf70305e03f69d6d4..0000000000000000000000000000000000000000
--- a/Source/core/frame/FrameDestructionObserver.cpp
+++ /dev/null
@@ -1,43 +0,0 @@
-/*
- * Copyright (C) 2011 Google, Inc. All Rights Reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY GOOGLE INC. ``AS IS'' AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "config.h"
-#include "core/frame/FrameDestructionObserver.h"
-
-#include "core/frame/LocalFrame.h"
-
-namespace blink {
-
-FrameDestructionObserver::FrameDestructionObserver(LocalFrame* frame)
-{
-    setContext(frame);
-}
-
-void FrameDestructionObserver::willDetachFrameHost()
-{
-    // Subclasses should override this function to handle this notification.
-}
-
-} // namespace blink