Enable lowmemorykiler trace event toggling.

Enable writing of events/lowmemorykiller/enable.

Bug: 38457440
Test: Tested writability of flag via Traceur apk
Change-Id: Ic138062e9667aa66412388046dea37236a7efd49

private/file_contexts

@@ -495,6 +495,7 @@
 /sys/kernel(/debug)?/tracing/events/vmscan/mm_vmscan_direct_reclaim_end/enable      u:object_r:tracing_shell_writable:s0
 /sys/kernel(/debug)?/tracing/events/vmscan/mm_vmscan_kswapd_sleep/enable            u:object_r:tracing_shell_writable:s0
 /sys/kernel(/debug)?/tracing/events/vmscan/mm_vmscan_kswapd_wake/enable             u:object_r:tracing_shell_writable:s0
+/sys/kernel(/debug)?/tracing/events/lowmemorykiller/enable                          u:object_r:tracing_shell_writable:s0
 /sys/kernel(/debug)?/tracing/instances(/.*)?                                        u:object_r:debugfs_tracing_instances:s0
 /sys/kernel(/debug)?/tracing/instances/wifi/free_buffer                             u:object_r:debugfs_wifi_tracing:s0
 /sys/kernel(/debug)?/tracing/instances/wifi/trace                                   u:object_r:debugfs_wifi_tracing:s0