[Files ranking] Don't warm the cache of Drive files on init.

Because the Drive QuickAccess API starts up quite slowly, our attempt
to warm the cache almost always fails. Let's remove it.

Bug: 1011221
Change-Id: I59b4d3c1a24a81f5c343dd8d26c1f15442fe9876
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1861796
Auto-Submit: Tony Yeoman <tby@chromium.org>
Reviewed-by: Jia Meng <jiameng@chromium.org>
Commit-Queue: Tony Yeoman <tby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706194}

chrome/browser/ui/app_list/search/drive_quick_access_provider.cc

@@ -77,9 +77,6 @@ DriveQuickAccessProvider::DriveQuickAccessProvider(Profile* profile)
   task_runner_ = base::CreateSequencedTaskRunner(
       {base::ThreadPool(), base::TaskPriority::BEST_EFFORT, base::MayBlock(),
        base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN});
-
-  // Warm up the cache.
-  AppListShown();
 }
 
 DriveQuickAccessProvider::~DriveQuickAccessProvider() = default;