binding: Window-returning attributes return null if a Window is detached.

third_party/WebKit/Source/core/frame/DOMWindow.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/frame/DOMWindow.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/dom/SecurityContext.h"
@@ skipping 85 matching lines @@
     // FIXME: Use FrameTree to get opener as well, to simplify logic here.
     if (!frame() || !frame()->client())
         return nullptr;
 
     Frame* opener = frame()->client()->opener();
     return opener ? opener->domWindow() : nullptr;
 }
 
 DOMWindow* DOMWindow::parent() const
 {
-    if (!frame())
+    // TODO(yukishiino): The 'parent' attribute must return |this|
+    // (the WindowProxy object of the browsing context itself) when it's
+    // top-level or detached.
+    if (!isCurrentlyDisplayedInFrame())
         return nullptr;
 
     Frame* parent = frame()->tree().parent();
     return parent ? parent->domWindow() : frame()->domWindow();
 }
 
 DOMWindow* DOMWindow::top() const
 {
-    if (!frame())
+    // TODO(yukishiino): The 'top' attribute must return |this|
+    // (the WindowProxy object of the browsing context itself) when it's
+    // top-level or detached.
+    if (!isCurrentlyDisplayedInFrame())
         return nullptr;
 
     return frame()->tree().top()->domWindow();
 }
 
 DOMWindow* DOMWindow::anonymousIndexedGetter(uint32_t index) const
 {
     if (!frame())
         return nullptr;
 
@@ skipping 242 matching lines @@
     page->focusController().focusDocumentView(frame(), true /* notifyEmbedder */);
 }
 
 DEFINE_TRACE(DOMWindow)
 {
     visitor->trace(m_location);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace blink