Add a Callback to Snackbar

BUG: 21553485
Change-Id: I465ec53a7479979da0dbe464913658e1d1bf3b63
diff --git a/design/api/current.txt b/design/api/current.txt
index 8009a89..0ccb120 100644
--- a/design/api/current.txt
+++ b/design/api/current.txt
@@ -219,6 +219,7 @@
     method public android.support.design.widget.Snackbar setAction(java.lang.CharSequence, android.view.View.OnClickListener);
     method public android.support.design.widget.Snackbar setActionTextColor(android.content.res.ColorStateList);
     method public android.support.design.widget.Snackbar setActionTextColor(int);
+    method public void setCallback(android.support.design.widget.Snackbar.Callback);
     method public android.support.design.widget.Snackbar setDuration(int);
     method public android.support.design.widget.Snackbar setText(java.lang.CharSequence);
     method public android.support.design.widget.Snackbar setText(int);
@@ -227,6 +228,12 @@
     field public static final int LENGTH_SHORT = -1; // 0xffffffff
   }
 
+  public static abstract class Snackbar.Callback {
+    ctor public Snackbar.Callback();
+    method public void onDismissed(android.support.design.widget.Snackbar);
+    method public void onShown(android.support.design.widget.Snackbar);
+  }
+
   public class SwipeDismissBehavior extends android.support.design.widget.CoordinatorLayout.Behavior {
     ctor public SwipeDismissBehavior();
     method public int getDragState();