Fix Android unit_tests failures with PlzNavigate.

content/browser/frame_host/navigation_request.cc

Index: content/browser/frame_host/navigation_request.cc
diff --git a/content/browser/frame_host/navigation_request.cc b/content/browser/frame_host/navigation_request.cc
index bf8c9444a5cb7d18aedb5713730a2206ede76713..9a41726e51cbb034af54691e4627c0ddfeaeae80 100644
--- a/content/browser/frame_host/navigation_request.cc
+++ b/content/browser/frame_host/navigation_request.cc
@@ -520,6 +520,9 @@ void NavigationRequest::OnStartChecksComplete(
     NavigationThrottle::ThrottleCheckResult result) {
   CHECK(result != NavigationThrottle::DEFER);
 
+  if (on_start_checks_complete_closure_)
+    on_start_checks_complete_closure_.Run();
+
   // Abort the request if needed. This will destroy the NavigationRequest.
   if (result == NavigationThrottle::CANCEL_AND_IGNORE ||
       result == NavigationThrottle::CANCEL) {