Migrate off BrowserThread::DeleteSoon in /ios/chrome/browser/browser_state

Instead use base::DeleteSoon which enforces usage of TaskTraits.

This CL is a no-op as-is. It was recently discovered however that some
callers did BrowserThread::DeleteSoon() with pending tasks running on
different task queues (different traits  -- e.g.

TaskTraits to make this more obvious. Please review whether calls in
this CL can be migrated as-is or need additional traits to match
potentially pending tasks.

Split from https://chromium-review.googlesource.com/c/chromium/src/+/1894109
for cursory review.

This CL was uploaded by git cl split.

R=sdefresne@chromium.org


TaskPriority: :BEST_EFFORT) which can result in out-of-order deletion...
BrowserThread: :DeleteSoon() is being migrated to base::DeleteSoon() w/
Bug: 1019767
Change-Id: Iccc6ccf09b2e15f52c75ddba0ec63ff3e927efa8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1894884
Auto-Submit: Gabriel Charette <gab@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712406}

ios/chrome/browser/browser_state/chrome_browser_state_io_data.mm

@@ -391,7 +391,7 @@ void ChromeBrowserStateIOData::ShutdownOnUIThread(
     }
   }
 
-  bool posted = web::WebThread::DeleteSoon(web::WebThread::IO, FROM_HERE, this);
+  bool posted = base::DeleteSoon(FROM_HERE, {web::WebThread::IO}, this);
   if (!posted)
     delete this;
 }