FrameTree::Find only searches relative to local frames.

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

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
@@ skipping 514 matching lines @@
   DCHECK(GetDocument());
   GetEditor().Clear();
   GetEventHandler().Clear();
   Selection().DocumentAttached(GetDocument());
   GetInputMethodController().DocumentAttached(GetDocument());
   GetSpellChecker().DocumentAttached(GetDocument());
   if (IsMainFrame())
     has_received_user_gesture_ = false;
 }
 
+Frame* LocalFrame::FindFrameForNavigation(const AtomicString& name,
+                                          LocalFrame& active_frame) {
+  Frame* frame = Tree().Find(name);
+  if (!frame || !active_frame.CanNavigate(*frame))
+    return nullptr;
+  return frame;
+}
+
 LocalWindowProxy* LocalFrame::WindowProxy(DOMWrapperWorld& world) {
   return ToLocalWindowProxy(Frame::GetWindowProxy(world));
 }
 
 LocalDOMWindow* LocalFrame::DomWindow() const {
   return ToLocalDOMWindow(dom_window_);
 }
 
 void LocalFrame::SetDOMWindow(LocalDOMWindow* dom_window) {
   if (dom_window)
@@ skipping 650 matching lines @@
     node = GetDocument()->FocusedElement();
   }
 
   if (node) {
     return node->GetWebPluginContainerBase();
   }
   return nullptr;
 }
 
 }  // namespace blink