[Prerender] Restore request priorities when swapped in

content/browser/loader/resource_scheduler.cc

Index: content/browser/loader/resource_scheduler.cc
diff --git a/content/browser/loader/resource_scheduler.cc b/content/browser/loader/resource_scheduler.cc
index e1dcb0aa04ae1c3f52ee34e4c4ee2f09ced62df1..d653c7246944fb8f084e2f3d9ee437e13ba22e9f 100644
--- a/content/browser/loader/resource_scheduler.cc
+++ b/content/browser/loader/resource_scheduler.cc
@@ -237,8 +237,9 @@ class ResourceScheduler::ScheduledResourceRequest : public ResourceThrottle {
   }
 
   static ScheduledResourceRequest* ForRequest(net::URLRequest* request) {
-    return static_cast<UnownedPointer*>(request->GetUserData(kUserDataKey))
-        ->get();
+    UnownedPointer* pointer =
+        static_cast<UnownedPointer*>(request->GetUserData(kUserDataKey));
+    return pointer ? pointer->get() : nullptr;
   }
 
   // Starts the request. If |start_mode| is START_ASYNC, the request will not
@@ -1080,6 +1081,17 @@ void ResourceScheduler::ReprioritizeRequest(net::URLRequest* request,
                               new_priority_params);
 }
 
+void ResourceScheduler::ReprioritizeRequest(net::URLRequest* request,
+                                            net::RequestPriority new_priority) {
+  int current_intra_priority = 0;
+  auto* existing_request = ScheduledResourceRequest::ForRequest(request);
+  if (existing_request) {
+    current_intra_priority =
+        existing_request->get_request_priority_params().intra_priority;
+  }
+  ReprioritizeRequest(request, new_priority, current_intra_priority);
+}
+
 ResourceScheduler::ClientId ResourceScheduler::MakeClientId(
     int child_id, int route_id) {
   return (static_cast<ResourceScheduler::ClientId>(child_id) << 32) | route_id;