Sequential focus navigation across frames should clear per-document starting point.

third_party/WebKit/Source/core/page/FocusController.cpp

Index: third_party/WebKit/Source/core/page/FocusController.cpp
diff --git a/third_party/WebKit/Source/core/page/FocusController.cpp b/third_party/WebKit/Source/core/page/FocusController.cpp
index b0d99db2001cebe42ace8ba1a6c558b02fe1d64b..b12d00e65daf5be5c67ba009d8722122e1bcb590 100644
--- a/third_party/WebKit/Source/core/page/FocusController.cpp
+++ b/third_party/WebKit/Source/core/page/FocusController.cpp
@@ -994,6 +994,7 @@ bool FocusController::advanceFocusInDocumentOrder(LocalFrame* frame, Element* st
     if (&newDocument != document) {
         // Focus is going away from this document, so clear the focused element.
         document->clearFocusedElement();
+        document->setSequentialFocusNavigationStartingPoint(nullptr);
     }
 
     setFocusedFrame(newDocument.frame());