Migrate emergency default app to role manager.

Bug: 123293861
Test: atest DefaultEmergencyPickerTest
Change-Id: I7ca729fa457c23ba7a3e7a00f271a601cd124290
diff --git a/services/core/java/com/android/server/policy/role/LegacyRoleResolutionPolicy.java b/services/core/java/com/android/server/policy/role/LegacyRoleResolutionPolicy.java
index 888dd99..77bf930 100644
--- a/services/core/java/com/android/server/policy/role/LegacyRoleResolutionPolicy.java
+++ b/services/core/java/com/android/server/policy/role/LegacyRoleResolutionPolicy.java
@@ -130,6 +130,12 @@
                 String packageName = componentName != null ? componentName.getPackageName() : null;
                 return CollectionUtils.singletonOrEmpty(packageName);
             }
+            case RoleManager.ROLE_EMERGENCY: {
+                String defaultEmergencyApp = Settings.Secure.getStringForUser(
+                        mContext.getContentResolver(),
+                        Settings.Secure.EMERGENCY_ASSISTANCE_APPLICATION, userId);
+                return CollectionUtils.singletonOrEmpty(defaultEmergencyApp);
+            }
             default: {
                 Slog.e(LOG_TAG, "Don't know how to find legacy role holders for " + roleName);
                 return Collections.emptyList();