[multiball] Minimize code in startUpChromeUI.

Moves some process-scoped code from
-startUpChromeUIPostCrash:needRestoration:

* Break down scheduleTasksRequiringBVCWithBrowserState to not include
promo-related code. Promo logic will move to Scene.
* Move some calls to startUpAfterFirstWindowCreated

Bug: 1045658
Change-Id: Iab374d1fc4befedf1f51713d13e00ba4d108c02d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2087334
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747173}

ios/chrome/app/main_controller.mm

@@ -594,6 +594,14 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
 // This initialization must only happen once there's at least one Chrome window
 // open.
 - (void)startUpAfterFirstWindowCreated {
+  // "Low priority" tasks
+  [_startupTasks registerForApplicationWillResignActiveNotification];
+  [self registerForOrientationChangeNotifications];
+
+  _launchOptions = nil;
+
+  [self scheduleTasksRequiringBVCWithBrowserState];
+
   CustomizeUIAppearance();
 
   [self scheduleStartupCleanupTasks];
@@ -638,16 +646,11 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
         [[CrashRestoreHelper alloc] initWithBrowser:self.mainBrowser];
   }
 
-  // "Low priority" tasks
-  [_startupTasks registerForApplicationWillResignActiveNotification];
-  [self registerForOrientationChangeNotifications];
-
   [self.sceneController openTabFromLaunchOptions:_launchOptions
                               startupInformation:self
                                         appState:self.appState];
-  _launchOptions = nil;
 
-  [self scheduleTasksRequiringBVCWithBrowserState];
+  [self scheduleShowPromo];
 
   // Before bringing up the UI, make sure the launch mode is correct, and
   // check for previous crashes.
@@ -1124,7 +1127,6 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
             base::TimeDelta::FromSeconds(kExternalFilesCleanupDelaySeconds),
             base::OnceClosure());
   }
-  [self scheduleShowPromo];
 }
 
 - (void)scheduleDeleteDownloadsDirectory {