Expose isInEmergencySmsMode as @SystemApi.

Test: build
Bug: 173561006
Change-Id: I3ea87b789b90c606bc04c81a1a6b59fc49f65cc6
diff --git a/core/api/system-current.txt b/core/api/system-current.txt
index 6cf93fc..c2794d2 100644
--- a/core/api/system-current.txt
+++ b/core/api/system-current.txt
@@ -10844,6 +10844,7 @@
     method @RequiresPermission(android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE) public boolean isEmergencyAssistanceEnabled();
     method @RequiresPermission(android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE) @WorkerThread public boolean isIccLockEnabled();
     method @Deprecated @RequiresPermission(anyOf={android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE, android.Manifest.permission.READ_PHONE_STATE}) public boolean isIdle();
+    method @RequiresPermission(android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE) public boolean isInEmergencySmsMode();
     method @RequiresPermission(android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE) public boolean isLteCdmaEvdoGsmWcdmaEnabled();
     method @RequiresPermission(android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE) public boolean isMobileDataPolicyEnabled(int);
     method public boolean isNrDualConnectivityEnabled();
diff --git a/telephony/java/android/telephony/TelephonyManager.java b/telephony/java/android/telephony/TelephonyManager.java
index 683f200..e7a99d9 100644
--- a/telephony/java/android/telephony/TelephonyManager.java
+++ b/telephony/java/android/telephony/TelephonyManager.java
@@ -8139,6 +8139,7 @@
      *
      * @hide
      */
+    @SystemApi
     @RequiresPermission(android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE)
     public boolean isInEmergencySmsMode() {
         try {