FrameTree::Find only searches relative to local frames.

third_party/WebKit/Source/web/WebLocalFrameImpl.cpp

Index: third_party/WebKit/Source/web/WebLocalFrameImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebLocalFrameImpl.cpp b/third_party/WebKit/Source/web/WebLocalFrameImpl.cpp
index 25513bd30a24152b3a9ae62443c657a1b4278e4c..c5626ba0a5bd1df898431072e09daec99f058ec3 100644
--- a/third_party/WebKit/Source/web/WebLocalFrameImpl.cpp
+++ b/third_party/WebKit/Source/web/WebLocalFrameImpl.cpp
@@ -2016,6 +2016,11 @@ WebLocalFrameImpl* WebLocalFrameImpl::LocalRoot() {
   return local_root;
 }
 
+WebFrame* WebLocalFrameImpl::FindFrameByName(const WebString& name) {
+  Frame* result = GetFrame()->Tree().Find(name);
+  return WebFrame::FromFrame(result);
+}
+
 void WebLocalFrameImpl::SendPings(const WebURL& destination_url) {
   DCHECK(GetFrame());
   DCHECK(context_menu_node_.Get());