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

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

Index: third_party/WebKit/Source/core/frame/DOMWindow.cpp
diff --git a/third_party/WebKit/Source/core/frame/DOMWindow.cpp b/third_party/WebKit/Source/core/frame/DOMWindow.cpp
index e871c8ecf676f20c475382f282e344ecf1c897e5..233d4e4736d575c1c847afdf66ea1a830fb0d5b8 100644
--- a/third_party/WebKit/Source/core/frame/DOMWindow.cpp
+++ b/third_party/WebKit/Source/core/frame/DOMWindow.cpp
@@ -103,7 +103,10 @@ DOMWindow* DOMWindow::opener() const
 
 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();
@@ -112,7 +115,10 @@ DOMWindow* DOMWindow::parent() const
 
 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();