FlingTracker can divide by zero and hang StatusBar in an infinite loop

if 2 events have the same timestamp then FlingTracker in PanelView will divide
by zero causing NaNs. the bug is usually triggered by rapid StatusBar up/down
dragging activity and updateCarrierLabelVisibility can then loop indefinitely
looking at NaNs. the user visible symptom is that StatusBar refuses to pull
down and is burning cpu time.

Signed-off-by: Michael Bestas <mikeioannina@gmail.com>

Change-Id: I0791c6bea953bf03346185fc6aaf44aaea79aace
IME : Fix sym key regression

http://review.cyanogenmod.org/#/c/25787/2 caused the "dismiss" arrow
for ime's to execute back action as well. Reproducible via :

Open sms app->Open message thread->Tap message field->Tap downward arrow on navbar

Expected behaviour : Keyboard should be dismissed
Actual behaviour : Keyboard is dismissed and user is taken to previous screen.

Change-Id: I6ab65b00464fb6e00849d7fd6c8bd438b23ee76b
Merge "FlingTracker can divide by zero and hang StatusBar in an infinite loop" into cm-10.1
Merge remote-tracking branch 'cm/cm-10.1' into cm-10.1