PhoneWindowManager: Don't handle navigation bar visibility when switching to PIE

Right now when restoring full height after disabling immersive if pie mode is
on, navbar isn't showed until panel collapsing cause it should have been showed
(the view even with height zero) called by top swipe gesture that calls requestTransientBars().
Don't touch the API, cleanup old code traces and changes cause in any case navbar has height = 0
and its bottom/right gesture is disabled.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
Change-Id: Id05175a553aad2a5a2b36c3fe4e32a2d071dcc88
SystemUI: prevent NPE on clear recents double press

Pressing Clear all button twice fast or while the list
is clearing but not yet fully cleared causes sysui to crash due to
mRecentTaskDescriptions being null: (http://pastebin.com/2gRFvf8k)

Change-Id: I23d10edfd336041739fe80352ee01987e671dbd7
PIE: On-The-Spot: Fix abnormal behavior when chosing ASK_LATER

Right now when chosing ask later it does not activate default immersive for that immersion.
We should call switchImmersiveGlobal() no matter what we chose on on-the-spot dialog,
also if immersive mode is disabled and is going to be activated.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
NotificationHelper: We shouldn't use logical here, one case is enough no matter the order

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>