mm: support max-ram-size experiment

Use the experiment property to write configurations into the misc
partition so the bootloader can apply it next boot.

setprop persist.device_config.vendor_system_native_boot.max_ram_size 8192
setprop persist.device_config.vendor_system_native_boot.max_ram_size -1

Bug: 279871595
Test: set property and check max-ram-size in bootloader and reboot
Change-Id: I417eadff3d3e48b9e4054b23b6c79b5e514b99ba
diff --git a/mm/pixel-mm-gki.rc b/mm/pixel-mm-gki.rc
index 798406b..52603d5 100644
--- a/mm/pixel-mm-gki.rc
+++ b/mm/pixel-mm-gki.rc
@@ -69,3 +69,11 @@
 
 on property:init.svc.bugreportd=stopped
     write /sys/kernel/tracing/instances/pixel/tracing_on 1
+
+# max-ram-size experiment
+service vendor.set_max_ram_size /vendor/bin/misc_writer --set-max-ram-size ${persist.device_config.vendor_system_native_boot.max_ram_size:--1}
+    disabled
+    oneshot
+
+on property:persist.device_config.vendor_system_native_boot.max_ram_size=*
+    start vendor.set_max_ram_size