KeyChain: return null instead of throw

The API documentation says it will return null if the key isn't found.
We get null back from the keystore daemon when it can't retrieve the
data, so just return null back to the API caller.

Change-Id: I42248bd50cbc5f76864bd762aae3faab1c50529d
Applying ChannelScrolling to remove calculateDragAngle

To avoid angle calculation changed the logic to use virtual areas.
When try to drag or pan, check where the current touch point locates
and determine how to drag a page.

Change-Id: Id9bd08a69c4ac93ff385c8088e6c16bed5dc5f88
Signed-off-by: kiwon <kiwon98.lee@samsung.com>
avoid multiple-"0" to exceed the length of upper bound

Limits number of "0"s not to exceed length of maximum number allowed
for the NumberPicker.

Steps to reproduce:
1. Settings -> Date & time -> uncheck "Automatic date & time"
2. Select "Set time"
3. Select Time Area on Set time dialog
4. insert 00000000 via NumberPicker

Bug: 8073759
Change-Id: I0f3f5303d9a4b559217adb436f244407a23e58c0