Unhide @FunctionalInterface

Bug: 26623636
(cherry-picked from commit c5064327eae625b67013736048e35388decce52b)
Change-Id: I05fc731356891c4fdba79701b1b87384841d56ca
diff --git a/api/current.txt b/api/current.txt
index b4ba7d5..5960119 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -48430,6 +48430,9 @@
     field public static final java.lang.Class<java.lang.Float> TYPE;
   }
 
+  public abstract class FunctionalInterface implements java.lang.annotation.Annotation {
+  }
+
   public class IllegalAccessError extends java.lang.IncompatibleClassChangeError {
     ctor public IllegalAccessError();
     ctor public IllegalAccessError(java.lang.String);
diff --git a/api/system-current.txt b/api/system-current.txt
index ea7275e..8ffd512 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -51048,6 +51048,9 @@
     field public static final java.lang.Class<java.lang.Float> TYPE;
   }
 
+  public abstract class FunctionalInterface implements java.lang.annotation.Annotation {
+  }
+
   public class IllegalAccessError extends java.lang.IncompatibleClassChangeError {
     ctor public IllegalAccessError();
     ctor public IllegalAccessError(java.lang.String);