Make getNetworkSpecifier() public API.

The builder lets clients set it, and this may be useful for
unit tests of apps. It should be public.
The need arises from uses of this in WiFi and Telephony
network factories.

Test: build
Bug: 135998869
Change-Id: I57279cac139c28e8654d2066ba0c60edd1e6cd98
diff --git a/core/java/android/net/NetworkRequest.java b/core/java/android/net/NetworkRequest.java
index 4270740..471b23e 100644
--- a/core/java/android/net/NetworkRequest.java
+++ b/core/java/android/net/NetworkRequest.java
@@ -17,6 +17,7 @@
 package android.net;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
 import android.annotation.UnsupportedAppUsage;
@@ -461,6 +462,14 @@
         return networkCapabilities.hasTransport(transportType);
     }
 
+    /**
+     * @see Builder#setNetworkSpecifier(NetworkSpecifier)
+     */
+    @Nullable
+    public NetworkSpecifier getNetworkSpecifier() {
+        return networkCapabilities.getNetworkSpecifier();
+    }
+
     public String toString() {
         return "NetworkRequest [ " + type + " id=" + requestId +
                 (legacyType != ConnectivityManager.TYPE_NONE ? ", legacyType=" + legacyType : "") +