Promote VmSocketAddress as public API

Bug: 201676316
Test: libcore.android.system.OsTest#test_VmSocket though the test
doesn't seem to talk to the host. Thus, no additional permission is
needed to run the test.

Change-Id: I03753e42faa104e15ba028c52fec495c80719da2
diff --git a/api/current.txt b/api/current.txt
index 0f46df2..e584267 100755
--- a/api/current.txt
+++ b/api/current.txt
@@ -726,6 +726,12 @@
     field public final String version;
   }
 
+  public final class VmSocketAddress extends java.net.SocketAddress {
+    ctor public VmSocketAddress(int, int);
+    method public int getSvmCid();
+    method public int getSvmPort();
+  }
+
 }
 
 package dalvik.annotation {