Add isSmallBatteryDevice flag to ActivityManager.

Bug: 37351903
Change-Id: I6fed08c35474b10987388070eafb7b16e6944638
(cherry picked from commit 15eb998e65)

core/java/android/app/ActivityManager.java

@@ -1111,6 +1111,18 @@ public class ActivityManager {
         return RoSystemProperties.CONFIG_LOW_RAM;
     }
 
+    /**
+     * Returns true if this is a small battery device. Exactly whether a device is considered to be
+     * small battery is ultimately up to the device configuration, but currently it generally means
+     * something in the class of a device with 1000 mAh or less. This is mostly intended to be used
+     * to determine whether certain features should be altered to account for a drastically smaller
+     * battery.
+     * @hide
+     */
+    public static boolean isSmallBatteryDevice() {
+        return RoSystemProperties.CONFIG_SMALL_BATTERY;
+    }
+
     /**
      * Used by persistent processes to determine if they are running on a
      * higher-end device so should be okay using hardware drawing acceleration