Hide toolbar in RL screen when opened with no items.

The hiding/showing is normally done via
ReadingListListViewControllerAudience but the initial
setup is done before the navigationController was create.
It is necessary to create the navigationController in the
correct state.

Bug: 1128059
Change-Id: I2303356c71bf70f178a5f9a5c65f023750ecf05d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2414273Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Auto-Submit: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807841}

ios/chrome/browser/ui/reading_list/reading_list_coordinator.mm

@@ -137,7 +137,11 @@
   // Present RecentTabsNavigationController.
   self.navigationController = [[TableViewNavigationController alloc]
       initWithTable:self.tableViewController];
-  self.navigationController.toolbarHidden = NO;
+
+  // The initial call to |readingListHasItems:| may have been received before
+  // all UI elements were initialized. Call the callback directly to set up
+  // everything correctly.
+  [self readingListHasItems:self.mediator.hasElements];
 
   BOOL useCustomPresentation = YES;
   if (IsCollectionsCardPresentationStyleEnabled()) {