FrameTree::Find only searches relative to local frames.

third_party/WebKit/public/web/WebLocalFrame.h

Index: third_party/WebKit/public/web/WebLocalFrame.h
diff --git a/third_party/WebKit/public/web/WebLocalFrame.h b/third_party/WebKit/public/web/WebLocalFrame.h
index 9296734f0a36adf1539b307f46caf5451785803b..1333c020c482d242d8748c60b486f7ba3e37ab5a 100644
--- a/third_party/WebKit/public/web/WebLocalFrame.h
+++ b/third_party/WebKit/public/web/WebLocalFrame.h
@@ -110,6 +110,13 @@ class WebLocalFrame : public WebFrame {
   // Get the highest-level LocalFrame in this frame's in-process subtree.
   virtual WebLocalFrame* LocalRoot() = 0;
 
+  // Returns the frame identified by the given name.  This method supports
+  // pseudo-names like _self, _top, and _blank.  It traverses the entire
+  // browsing instance containing this frame, looking for a frame that matches
+  // the given name (but note some caveats around browsing instance boundaries
+  // tracked in https://crbug.com/718489).
+  virtual WebFrame* FindFrameByName(const WebString& name) = 0;
+
   // Navigation Ping --------------------------------------------------------
 
   virtual void SendPings(const WebURL& destination_url) = 0;