Revert part of fix for b/7377776 to fix b/7411356.

This means the visual glitch is possible again, but reduced since
the layout transitions are disabled.

It's more important to bring back nav buttons for incoming calls
(for the secure, screen off case).

Bug: 7411356
Change-Id: I83005a77930ec7f70a613b3396f85ab1a5fdd96c

Author: John Spurlock

policy/src/com/android/internal/policy/impl/keyguard/KeyguardViewMediator.java

@@ -1306,13 +1306,6 @@ private void adjustStatusBarLocked() {
                 // (like recents). Temporary enable/disable (e.g. the "back" button) are
                 // done in KeyguardHostView.
                 flags |= StatusBarManager.DISABLE_RECENT;
-                if (!mScreenOn) {
-                    // Disable all navbar buttons on screen off.  The navigation bar will hide
-                    // these immediately to avoid seeing the end of layout transition animations
-                    // if quickly turning back on.
-                    flags |= StatusBarManager.DISABLE_HOME;
-                    flags |= StatusBarManager.DISABLE_BACK;
-                }
                 if (isSecure() || !ENABLE_INSECURE_STATUS_BAR_EXPAND) {
                     // showing secure lockscreen; disable expanding.
                     flags |= StatusBarManager.DISABLE_EXPAND;