Annotate @SystemApi with required permissions.

Most @SystemApi methods should be protected with system (or higher)
permissions, so annotate common methods with @RequiresPermission to
make automatic verification easier.

Verification is really only relevant when calling into system
services (where permissions checking can happen on the other side of
a Binder call), so annotate managers with the new @SystemService
annotation, which is now automatically documented.

This is purely a docs change; no logic changes are being made.

Test: make -j32 update-api && make -j32 offline-sdk-docs
Bug: 62263906
Change-Id: I2554227202d84465676aa4ab0dd336b5c45fc651
diff --git a/core/java/android/net/nsd/NsdManager.java b/core/java/android/net/nsd/NsdManager.java
index 1dde3ca..2d480a1 100644
--- a/core/java/android/net/nsd/NsdManager.java
+++ b/core/java/android/net/nsd/NsdManager.java
@@ -17,6 +17,7 @@
 package android.net.nsd;
 
 import android.annotation.SdkConstant;
+import android.annotation.SystemService;
 import android.annotation.SdkConstant.SdkConstantType;
 import android.content.Context;
 import android.os.Handler;
@@ -113,11 +114,9 @@
  * http://www.iana.org/form/ports-service. Existing services can be found at
  * http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml
  *
- * Get an instance of this class by calling {@link android.content.Context#getSystemService(String)
- * Context.getSystemService(Context.NSD_SERVICE)}.
- *
  * {@see NsdServiceInfo}
  */
+@SystemService(Context.NSD_SERVICE)
 public final class NsdManager {
     private static final String TAG = NsdManager.class.getSimpleName();
     private static final boolean DBG = false;