Add display panel low power mode global setting & mapping to sys property.

This will help us run P/H experiments by controlling display panel low
power mode system property through P/H.

Bug: 72121774
Test: Compile, boot taimen.
Change-Id: Id4c95bcd5616e9749f9dcc9d9f4773ffdad3e994

core/java/android/provider/Settings.java

@@ -10332,6 +10332,15 @@ public final class Settings {
          */
         public static final String FPS_DEVISOR = "fps_divisor";
 
+        /**
+         * Flag to enable or disable display panel low power mode (lpm)
+         * false -> Display panel power saving mode is disabled.
+         * true  -> Display panel power saving mode is enabled.
+         *
+         * @hide
+         */
+        public static final String DISPLAY_PANEL_LPM = "display_panel_lpm";
+
         /**
          * App standby (app idle) specific settings.
          * This is encoded as a key=value list, separated by commas. Ex:

core/tests/coretests/src/android/provider/SettingsBackupTest.java

@@ -17,9 +17,11 @@
 package android.provider;
 
 import static com.google.android.collect.Sets.newHashSet;
+
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.is;
+
 import static java.lang.reflect.Modifier.isFinal;
 import static java.lang.reflect.Modifier.isPublic;
 import static java.lang.reflect.Modifier.isStatic;
@@ -194,6 +196,7 @@ public class SettingsBackupTest {
                     Settings.Global.DEVICE_PROVISIONED,
                     Settings.Global.DEVICE_PROVISIONING_MOBILE_DATA_ENABLED,
                     Settings.Global.DISK_FREE_CHANGE_REPORTING_THRESHOLD,
+                    Settings.Global.DISPLAY_PANEL_LPM,
                     Settings.Global.DISPLAY_SCALING_FORCE,
                     Settings.Global.DISPLAY_SIZE_FORCED,
                     Settings.Global.DNS_RESOLVER_MAX_SAMPLES,

services/core/java/com/android/server/am/GlobalSettingsToPropertiesMapper.java

@@ -42,6 +42,7 @@ class GlobalSettingsToPropertiesMapper {
         {Settings.Global.SYS_VDSO, "sys.vdso"},
         {Settings.Global.FPS_DEVISOR, ThreadedRenderer.DEBUG_FPS_DIVISOR},
         {Settings.Global.UID_CPUPOWER, "uid.cpupower"},
+        {Settings.Global.DISPLAY_PANEL_LPM, "sys.display_panel_lpm"},
     };