Add a NavigationThrottle to the public content/ interface

content/browser/loader/navigation_resource_handler.cc

Index: content/browser/loader/navigation_resource_handler.cc
diff --git a/content/browser/loader/navigation_resource_handler.cc b/content/browser/loader/navigation_resource_handler.cc
index a01e7ef0796eb8b3e804eeb38195196406e29a92..62baab41c4c5324a4a00d87e5625431bf12b0b78 100644
--- a/content/browser/loader/navigation_resource_handler.cc
+++ b/content/browser/loader/navigation_resource_handler.cc
@@ -15,7 +15,10 @@
 #include "content/public/browser/stream_handle.h"
 #include "content/public/common/resource_response.h"
 #include "net/base/net_errors.h"
+#include "net/url_request/redirect_info.h"
 #include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context.h"
+#include "net/url_request/url_request_job_factory.h"
 
 namespace content {
 
@@ -62,7 +65,9 @@ bool NavigationResourceHandler::OnRequestRedirected(
   // TODO(davidben): Perform a CSP check here, and anything else that would have
   // been done renderer-side.
   DevToolsNetLogObserver::PopulateResponseInfo(request(), response);
-  core_->NotifyRequestRedirected(redirect_info, response);
+  bool is_external_protocol =
+      !request()->context()->job_factory()->IsHandledURL(redirect_info.new_url);
+  core_->NotifyRequestRedirected(redirect_info, response, is_external_protocol);
   *defer = true;
   return true;
 }