Custom message in AoD

Optional message that lives under the clock and also
in AoD. Implemented using a slice.

Test: launch sysui, look at the date in AoD
Test: runtest -x packages/SystemUI/tests/src/com/android/systemui/keyguard/KeyguardSliceProviderTest.java
Change-Id: I9dbc827bd48c6a3d1b25b0a481ffaecc0dd37f25
diff --git a/data/etc/privapp-permissions-platform.xml b/data/etc/privapp-permissions-platform.xml
index 2f9ae57..08df2eb 100644
--- a/data/etc/privapp-permissions-platform.xml
+++ b/data/etc/privapp-permissions-platform.xml
@@ -326,6 +326,7 @@
     <privapp-permissions package="com.android.systemui">
         <permission name="android.permission.BATTERY_STATS"/>
         <permission name="android.permission.BIND_APPWIDGET"/>
+        <permission name="android.permission.BIND_SLICE" />
         <permission name="android.permission.BLUETOOTH_PRIVILEGED"/>
         <permission name="android.permission.CHANGE_COMPONENT_ENABLED_STATE"/>
         <permission name="android.permission.CHANGE_DEVICE_IDLE_TEMP_WHITELIST"/>