Whitelist minui properties to be overridden by /vendor/default.prop.

These values will be read by platform module (/sbin/charger), and need
to be configurable by vendor init.

Bug: 113567255
Test: Build along with other CLs in the topic (for Makefile and
      libminui changes). Boot into charger mode.
Test: Boot into recovery. Run graphics test.
Change-Id: I5b272f345e2a5a255c2f660c59c1da3245aa1e03

public/property_contexts

@@ -114,6 +114,9 @@ ro.lmk.critical_upgrade u:object_r:exported3_default_prop:s0 exact bool
 ro.lmk.downgrade_pressure u:object_r:exported3_default_prop:s0 exact int
 ro.lmk.kill_heaviest_task u:object_r:exported3_default_prop:s0 exact bool
 ro.lmk.upgrade_pressure u:object_r:exported3_default_prop:s0 exact int
+ro.minui.default_rotation u:object_r:exported3_default_prop:s0 exact string
+ro.minui.overscan_percent u:object_r:exported3_default_prop:s0 exact int
+ro.minui.pixel_format u:object_r:exported3_default_prop:s0 exact string
 ro.oem_unlock_supported u:object_r:exported3_default_prop:s0 exact int
 ro.opengles.version u:object_r:exported3_default_prop:s0 exact int
 ro.radio.noril u:object_r:exported3_default_prop:s0 exact string