Enable Update Password UI on iOS behind a flag

ios/chrome/browser/experimental_flags.mm

 // Copyright 2015 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.
 
 // This file can be empty. Its purpose is to contain the relatively short lived
 // definitions required for experimental flags.
 
 #include "ios/chrome/browser/experimental_flags.h"
 
 #include <dispatch/dispatch.h>
 #import <Foundation/Foundation.h>
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_util.h"
 #include "components/autofill/core/common/autofill_switches.h"
 #include "components/variations/variations_associated_data.h"
 #include "ios/chrome/browser/chrome_switches.h"
 #include "ios/web/public/web_view_creation_util.h"
 
 namespace {
 NSString* const kEnableAlertOnBackgroundUpload =
     @"EnableAlertsOnBackgroundUpload";
 NSString* const kEnableViewCopyPasswords = @"EnableViewCopyPasswords";
 NSString* const kHeuristicsForPasswordGeneration =
     @"HeuristicsForPasswordGeneration";
 NSString* const kEnableReadingList = @"EnableReadingList";
+NSString* const kUpdatePasswordUIEnabled = @"UpdatePasswordUIEnabled";
 }  // namespace
 
 namespace experimental_flags {
 
 bool IsAlertOnBackgroundUploadEnabled() {
   return [[NSUserDefaults standardUserDefaults]
       boolForKey:kEnableAlertOnBackgroundUpload];
 }
 
 bool IsLRUSnapshotCacheEnabled() {
@@ skipping 89 matching lines @@
     return false;
   }
 
   // Check if the finch experiment is turned on
   std::string group_name =
       base::FieldTrialList::FindFullName("PhysicalWebEnabled");
   return base::StartsWith(group_name, "Enabled",
                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
+bool IsUpdatePasswordUIEnabled() {
+  return [[NSUserDefaults standardUserDefaults]
+      boolForKey:kUpdatePasswordUIEnabled];
+}
+
 }  // namespace experimental_flags