Use DesktopModeStatus#canEnterDesktopMode instead of just Flag check.

This reverts commit 687817ebebd68d979c0749c49a211a4d2a53570a. Which was
an incorrect revert.

Test: Existing tests pass
Bug: 349544589
Flag: EXEMPT minor refactoring

Change-Id: Ibf69ca67e313850d7afbcd6661da50cc76011c42
3 files changed