libcutils: android_reboot: add thermal shutdown command

Add ANDROID_RB_THERMOFF command to android_reboot(), denoting a power
off due to thermal limits exceeded.  When this command is used, Android
may provide notification to the user about the potentially unexpected
power off at next boot.

Bug: 30994946
Test: Manual: setprop sys.powerctl thermal-shutdown
Change-Id: If2cde1b6a3c281a5750b50295412a4801ed5b2f2

libcutils/android_reboot.c

@@ -209,6 +209,10 @@ int android_reboot_with_callback(
                            LINUX_REBOOT_CMD_RESTART2, arg);
             break;
 
+        case ANDROID_RB_THERMOFF:
+            ret = reboot(RB_POWER_OFF);
+            break;
+
         default:
             ret = -1;
     }

libcutils/include/cutils/android_reboot.h

@@ -25,6 +25,7 @@ __BEGIN_DECLS
 #define ANDROID_RB_RESTART  0xDEAD0001
 #define ANDROID_RB_POWEROFF 0xDEAD0002
 #define ANDROID_RB_RESTART2 0xDEAD0003
+#define ANDROID_RB_THERMOFF 0xDEAD0004
 
 /* Properties */
 #define ANDROID_RB_PROPERTY "sys.powerctl"