[CM] Unhide the NetworkSpecifier as object API

API visibility change: unhide allowing NetworkSpecifier
to be an arbitrary object.

Bug: 27533960
Bug: 36053921
Bug: 36275276
Test: builds and runs
Change-Id: I1d1705cca7ece077ef8d7c674c62d5369fedbb03
diff --git a/core/java/android/net/NetworkSpecifier.java b/core/java/android/net/NetworkSpecifier.java
index 1b9e396..87a2b05 100644
--- a/core/java/android/net/NetworkSpecifier.java
+++ b/core/java/android/net/NetworkSpecifier.java
@@ -21,10 +21,11 @@
  *
  * Applications cannot instantiate this class by themselves, but can obtain instances of
  * subclasses of this class via other APIs.
- *
- * @hide
  */
 public abstract class NetworkSpecifier {
+    /** @hide */
+    public NetworkSpecifier() {}
+
     /**
      * Returns true if a request with this {@link NetworkSpecifier} is satisfied by a network
      * with the given NetworkSpecifier.