Add a callback for cancelling the context menu.

ui/base/ios/cru_context_menu_controller.mm

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ui/base/ios/cru_context_menu_controller.h"
 
 #include <algorithm>
 
 #include "base/ios/ios_util.h"
 #include "base/ios/weak_nsobject.h"
@@ skipping 250 matching lines @@
     void (^actionHandler)(UIAlertAction*) = ^(UIAlertAction* action) {
       [menuHolder performActionAtIndex:itemIndex];
       [weakSelf setVisible:NO];
     };
     [alert addAction:[UIAlertAction actionWithTitle:itemTitle
                                               style:UIAlertActionStyleDefault
                                             handler:actionHandler]];
   }];
 
   // Cancel button goes last, to match other browsers.
+  void (^cancelHandler)(UIAlertAction*) = ^(UIAlertAction* action) {
+    [weakSelf setVisible:NO];
+  };
   UIAlertAction* cancel_action =
       [UIAlertAction actionWithTitle:l10n_util::GetNSString(IDS_APP_CANCEL)
                                style:UIAlertActionStyleCancel
-                             handler:nil];
+                             handler:cancelHandler];
   [alert addAction:cancel_action];
 
   // Present sheet/popover using controller that is added to view hierarchy.
   UIViewController* topController = view.window.rootViewController;
   while (topController.presentedViewController)
     topController = topController.presentedViewController;
   [topController presentViewController:alert animated:YES completion:nil];
   self.visible = YES;
 }
 
 @end