bindDeviceAdminService requires service to be proected by BIND_DEVICE_ADMIN

Test: cts-tradefed cts-dev --module DevicePolicyManager  --test com.android.cts.devicepolicy.DeviceOwnerPlusProfileOwnerTest

Fix: 37624960

Change-Id: I0df88d2a019a0c5f8f997db1efede35a20441fa8
diff --git a/core/java/android/app/admin/DevicePolicyManager.java b/core/java/android/app/admin/DevicePolicyManager.java
index 7855b92..51deb87 100644
--- a/core/java/android/app/admin/DevicePolicyManager.java
+++ b/core/java/android/app/admin/DevicePolicyManager.java
@@ -7826,7 +7826,8 @@
      * See {@link #getBindDeviceAdminTargetUsers} for a definition of which
      * device/profile owners are allowed to bind to services of another profile/device owner.
      * <p>
-     * The service must be unexported. Note that the {@link Context} used to obtain this
+     * The service must be protected by {@link android.Manifest.permission#BIND_DEVICE_ADMIN}.
+     * Note that the {@link Context} used to obtain this
      * {@link DevicePolicyManager} instance via {@link Context#getSystemService(Class)} will be used
      * to bind to the {@link android.app.Service}.
      *