[performance_manager] Support kLoadedBusy->kLoading transition in BackgroundTabLoadingPolicy.

This transition can happen when a new load starts before the page
reaches quiescence after the previous load. Supporting it is the last
step before loading background tabs can be controlled from the
Performance Manager.

Bug: 1166745, 1059341
Change-Id: I0472af8388733dfc7e922a2d11a633499927517d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3271890
Reviewed-by: Chris Hamilton <[email protected]>
Reviewed-by: David Trainor <[email protected]>
Auto-Submit: François Doray <[email protected]>
Commit-Queue: David Trainor <[email protected]>
Cr-Commit-Position: refs/heads/main@{#941867}
diff --git a/chrome/browser/after_startup_task_utils.cc b/chrome/browser/after_startup_task_utils.cc
index f65aef7..f6e1d15 100644
--- a/chrome/browser/after_startup_task_utils.cc
+++ b/chrome/browser/after_startup_task_utils.cc
@@ -174,7 +174,8 @@
 
   // PageNodeObserver overrides
   void OnLoadingStateChanged(
-      const performance_manager::PageNode* page_node) override {
+      const performance_manager::PageNode* page_node,
+      performance_manager::PageNode::LoadingState previous_state) override {
     // Only interested in visible PageNodes
     if (page_node->IsVisible()) {
       if (page_node->GetLoadingState() ==