Fix Watchdog HeartbeatHandler to run on correct thread

The HeartbeatHandler for the System Server Watchdog has been running
on the wrong thread due to a race condition in initialization.  It's
designed to run on ServerThread, so that it can catch lockups in the
main looper of the System Server.  It has been running on
ActivityManagerThread instead, so it does not detect lockups on the
ServerThread as it should.

ActivityManagerService is calling Watchdog.getInstance() before
ServerThread calls Watchdog.getInstance().init(), so the handler is
being bound to the ActivityManagerThread instead of the ServerThread.

Explicitly bind HeartbeatHandler to ServerThread, so that the Watchdog
catches lockups on this critical thread.

Change-Id: Iccb184ac3adb817feb86ed4ee0e50e443bf74636
Email force close when pressing back key after selecting characters

Email and Browser will be forced closed after selecting a text
and then press the back key, tilting the screen or trying to
share or copy the text. This is because a previouse fix
is using a part of the code that Google has removed.
Fix: clearSelection will now use its own EventHub id,
CLEAR_SELECT_TEXT.

This part describes the previous fix.
Marking a text on the web page and then press copy works,
but trying to mark the same text again does not work.
The reason for this is that the selection never gets
cleared in webkit.
The fix, calling cleaSelection in the onDestroyActionMode.
Also added clearSelection when getting an
onConfigurationChange.

FIX=DMS01503793

Change-Id: I5e5673bac4efb3d28e9fc613da4bf636f8ab3c39
Keep keyboard lit until the screen is dimmed

Do not use button timeout for keyboard (which is intrusive on QWERTY
sliders). Keep it lit until the screen dims instead of turning it off
like the buttons after 5 seconds. Also consider setting keyboard
visibility as a user activity.