Clarify logic for showing CrostiniInstallerView.

This code now avoids a redundant check of crostini UI allowed.

Bug: None
Change-Id: I34c15883eccb2446b4cab0388ca479c7203ed65e
Reviewed-on: https://chromium-review.googlesource.com/c/1325273Reviewed-by: Renée Wright <rjwright@chromium.org>
Commit-Queue: Nicholas Verne <nverne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606353}

chrome/browser/chromeos/crostini/crostini_util.cc

@@ -315,8 +315,9 @@ void LaunchCrostiniApp(Profile* profile,
     DCHECK(files.empty());
     RecordAppLaunchHistogram(CrostiniAppLaunchAppType::kTerminal);
 
+    // At this point, we know that Crostini UI is allowed.
     if (!crostini_manager->IsCrosTerminaInstalled() ||
-        !IsCrostiniEnabled(profile)) {
+        !profile->GetPrefs()->GetBoolean(crostini::prefs::kCrostiniEnabled)) {
       ShowCrostiniInstallerView(profile, CrostiniUISurface::kAppList);
       return;
     }