FrameTree::Find only searches relative to local frames.

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

Index: third_party/WebKit/Source/core/frame/LocalFrame.cpp
diff --git a/third_party/WebKit/Source/core/frame/LocalFrame.cpp b/third_party/WebKit/Source/core/frame/LocalFrame.cpp
index 9c6d497d813e251155e59eb3d2bc51a9b97bbb35..18abbd55162cfb442ebd119b87f23975dff847d0 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrame.cpp
+++ b/third_party/WebKit/Source/core/frame/LocalFrame.cpp
@@ -531,6 +531,14 @@ void LocalFrame::DocumentAttached() {
     has_received_user_gesture_ = false;
 }
 
+Frame* LocalFrame::FindFrameForNavigation(const AtomicString& name,
+                                          Frame& 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));
 }