Keyguard: smooth background change.

Change-Id: Ia0e4d0000db72b5cdb6fede03791805e34fa311d

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardViewManager.java

Conflicts:

	packages/Keyguard/src/com/android/keyguard/KeyguardViewManager.java