Comment fix: say tablet mode

Ash immersive mode is not quite right anymore: remove it.

Bug: 839243
No-Try: true
Change-Id: If25f8e3411006c694825a38841fd1ae92f287623
Reviewed-on: https://chromium-review.googlesource.com/c/1336951Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608293}

chrome/browser/chromeos/file_manager/file_manager_browsertest_base.h

@@ -66,7 +66,7 @@ class FileManagerBrowserTestBase : public extensions::ExtensionApiTest {
   // Returns true if the test requires in guest mode.
   bool IsGuestModeTest() const { return GetGuestMode() == IN_GUEST_MODE; }
 
-  // Returns true if the test runs in tablet mode (aka Ash immersive mode).
+  // Returns true if the test runs in tablet mode.
   bool IsTabletModeTest() const { return GetTabletMode(); }
 
   // Returns true if the test requires DriveFS.