Shutdown device gracefully when net discharging

Instead of checking the presence of power supplies, check
battery status to determine whether it should
shutdown. In detail, shutdown if

battery level == 0 && status != charging

Change-Id: Ie3d93d305e40f2f45d60538e7831f00be0380544
Fixes: 115715604
Test: boots

services/core/java/com/android/server/BatteryService.java

@@ -356,10 +356,27 @@ public final class BatteryService extends SystemService {
                 && (oldPlugged || mLastBatteryLevel > mLowBatteryWarningLevel);
     }
 
+    private boolean shouldShutdownLocked() {
+        if (mHealthInfo.batteryLevel > 0) {
+            return false;
+        }
+
+        // Battery-less devices should not shutdown.
+        if (!mHealthInfo.batteryPresent) {
+            return false;
+        }
+
+        // If battery state is not CHARGING, shutdown.
+        // - If battery present and state == unknown, this is an unexpected error state.
+        // - If level <= 0 and state == full, this is also an unexpected state
+        // - All other states (NOT_CHARGING, DISCHARGING) means it is not charging.
+        return mHealthInfo.batteryStatus != BatteryManager.BATTERY_STATUS_CHARGING;
+    }
+
     private void shutdownIfNoPowerLocked() {
         // shut down gracefully if our battery is critically low and we are not powered.
         // wait until the system has booted before attempting to display the shutdown dialog.
-        if (mHealthInfo.batteryLevel == 0 && !isPoweredLocked(BatteryManager.BATTERY_PLUGGED_ANY)) {
+        if (shouldShutdownLocked()) {
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {