[Mac] Add a feature flag to disable Javascript execution in Applescript

chrome/browser/ui/cocoa/applescript/error_applescript.mm

 // Copyright (c) 2011 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 "chrome/browser/ui/cocoa/applescript/error_applescript.h"
 
 #include "base/logging.h"
 #include "chrome/grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
@@ skipping 31 matching lines @@
       break;
     case errInvalidTabIndex:
       error_string = GetNSString(IDS_INVALID_TAB_INDEX_APPLESCRIPT_MAC);
       break;
     case errSetMode:
       error_string = GetNSString(IDS_SET_MODE_APPLESCRIPT_MAC);
       break;
     case errWrongIndex:
       error_string = GetNSString(IDS_WRONG_INDEX_ERROR_APPLESCRIPT_MAC);
       break;
+    case errJavaScriptUnsupported:
+      error_string =
+          GetNSString(IDS_JAVASCRIPT_UNSUPPORTED_ERROR_APPLESCRIPT_MAC);
+      break;
     default:
       NOTREACHED();
   }
   [current_command setScriptErrorString:error_string];
 }