Clear the owner element's widget in Document::shutdown().

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

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index 196f562691e386f9bdd7377e29038afb9aec1869..2896d2e575ebe05ec804f4921434c031505111b0 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -351,8 +351,8 @@ void FrameView::dispose() {
   // FIXME: Do we need to do something here for OOPI?
   HTMLFrameOwnerElement* ownerElement = m_frame->deprecatedLocalOwner();
   // TODO(dcheng): It seems buggy that we can have an owner element that
-  // points to another Widget.
-  if (ownerElement && ownerElement->ownedWidget() == this)
+  // points to another Widget. See https://crbug.com/673170 for an example.

[esprehn, 2016/12/13 23:46:22]

Can we add a commented out DCHECK here with the widget condition you removed?
That way folks know what the comment is about. Also add the description you had
in the review for how we get there here.

[Mariusz Mlynski, 2016/12/14 00:18:03]

Done. The comment would logically better belong inside the if clause, but I
think it's more readable like this. Let me know if you prefer otherwise.

+  if (ownerElement)
     ownerElement->setWidget(nullptr);
 
 #if ENABLE(ASSERT)