Fix stale focusedElement in unloaded document.

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 2fde2c526802721659102806ad693fc66f3f70b6..285fd9e6c74aeb6ed02e9ba7f36a74cf571ce477 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -2644,6 +2644,10 @@ void Element::focus(const FocusParams& params) {
   if (!document().isActive())
     return;
 
+  if (isFrameOwnerElement() &&
+      toHTMLFrameOwnerElement(this)->contentDocument()->unloadStarted())

[tkent, 2017/02/17 07:34:00]

contnetDocument() might return nullptr.

+    return;
+
   document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
   if (!isFocusable())
     return;