API review: Metadata class not used.

The Metadata class doesn't actually seem to be used with anything
in the SDK, and the API probably needs some work, so hide it.

Change-Id: Ifecf49130b90cbb4c588ad8104f1e7957978f789

Author: Dianne Hackborn

api/current.txt

@@ -10869,16 +10869,6 @@ package android.media {
     method public abstract void onScanCompleted(java.lang.String, android.net.Uri);
   }
 
-  public class Metadata {
-    method public boolean getBoolean(int);
-    method public boolean has(int);
-    method public java.util.Set<java.lang.Integer> keySet();
-    field public static final int PAUSE_AVAILABLE = 1; // 0x1
-    field public static final int SEEK_AVAILABLE = 4; // 0x4
-    field public static final int SEEK_BACKWARD_AVAILABLE = 2; // 0x2
-    field public static final int SEEK_FORWARD_AVAILABLE = 3; // 0x3
-  }
-
   public class RemoteControlClient {
     ctor public RemoteControlClient(android.content.ComponentName);
     ctor public RemoteControlClient(android.content.ComponentName, android.os.Looper);

media/java/android/media/Metadata.java

@@ -39,6 +39,8 @@
 
    The caller is expected to know the type of the metadata and call
    the right get* method to fetch its value.
+   
+   @hide
  */
 public class Metadata
 {