Add a NavigationThrottle to the public content/ interface

content/browser/loader/navigation_url_loader_delegate.h

Index: content/browser/loader/navigation_url_loader_delegate.h
diff --git a/content/browser/loader/navigation_url_loader_delegate.h b/content/browser/loader/navigation_url_loader_delegate.h
index 62351aebf5fddcbc9c4ba4a07ab0cc4ace18c262..54247cff2f7ee0e2a8ba82c6eafb270461c39b03 100644
--- a/content/browser/loader/navigation_url_loader_delegate.h
+++ b/content/browser/loader/navigation_url_loader_delegate.h
@@ -26,7 +26,8 @@ class CONTENT_EXPORT NavigationURLLoaderDelegate {
   // processing the request.
   virtual void OnRequestRedirected(
       const net::RedirectInfo& redirect_info,
-      const scoped_refptr<ResourceResponse>& response) = 0;
+      const scoped_refptr<ResourceResponse>& response,
+      bool is_external_protocol) = 0;
 
   // Called when the request receives its response. No further calls will be
   // made to the delegate. The response body is returned as a stream in