PlzNavigate: Properly set the pending entry in the NavigatorImpl unit test.

content/browser/frame_host/navigation_controller_impl.cc

Index: content/browser/frame_host/navigation_controller_impl.cc
diff --git a/content/browser/frame_host/navigation_controller_impl.cc b/content/browser/frame_host/navigation_controller_impl.cc
index 0b0f411a1a041f52893e84357af935f7fe81c0df..f62c0a9cac80e5b8662be0506e22c36ec598ad7b 100644
--- a/content/browser/frame_host/navigation_controller_impl.cc
+++ b/content/browser/frame_host/navigation_controller_impl.cc
@@ -1760,6 +1760,11 @@ void NavigationControllerImpl::DiscardPendingEntry() {
   pending_entry_index_ = -1;
 }
 
+void NavigationControllerImpl::SetPendingEntryAndIndexForTesting(int index) {
+  pending_entry_index_ = index;
+  pending_entry_ = entries_[pending_entry_index_].get();
+}
+
 void NavigationControllerImpl::DiscardTransientEntry() {
   if (transient_entry_index_ == -1)
     return;