Re-enable the Cherry Pick button when cancelled

If the Cherry Pick dialog is cancelled, the Cherry Pick button
cannot be clicked again.

Change-Id: I5c2fb48ae4b01cfa122797b84a226cfb4ef6efe5
(cherry picked from commit 06810e758c7ea0eabf7ff43d785c65e2c90d1373)

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/CherryPickAction.java

diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/CherryPickAction.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/CherryPickAction.java
index 10d7297..6b44299 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/CherryPickAction.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/CherryPickAction.java
@@ -23,10 +23,14 @@
 import com.google.gerrit.common.PageLinks;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
+import com.google.gwt.event.logical.shared.CloseEvent;
 import com.google.gwt.user.client.ui.Button;
+import com.google.gwt.user.client.ui.FocusWidget;
+import com.google.gwt.user.client.ui.PopupPanel;
+
 
 class CherryPickAction {
-  static void call(Button b, final ChangeInfo info, final String revision,
+  static void call(final Button b, final ChangeInfo info, final String revision,
       String project, final String commitMessage) {
     // TODO Replace CherryPickDialog with a nicer looking display.
     b.setEnabled(false);
@@ -62,6 +66,12 @@
               }
             });
       }
+
+      @Override
+      public void onClose(CloseEvent<PopupPanel> event) {
+        super.onClose(event);
+        b.setEnabled(true);
+      }
     }.center();
   }
 }