Removed IsNativeAppLauncherEnabled() experiment

ios/chrome/browser/web/external_app_launcher.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 "ios/chrome/browser/web/external_app_launcher.h"
 
 #include "base/ios/ios_util.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/sys_string_conversions.h"
 #include "components/strings/grit/components_strings.h"
-#include "ios/chrome/browser/experimental_flags.h"
 #import "ios/chrome/browser/open_url_util.h"
 #import "ios/chrome/browser/web/mailto_url_rewriter.h"
 #include "ios/chrome/grit/ios_strings.h"
 #import "net/base/mac/url_conversions.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "url/gurl.h"
 #include "url/url_constants.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
@@ skipping 139 matching lines @@
     if (!linkClicked && UrlHasAppStoreScheme(gURL)) {
       NSString* prompt = l10n_util::GetNSString(IDS_IOS_OPEN_IN_ANOTHER_APP);
       NSString* openLabel =
           l10n_util::GetNSString(IDS_IOS_APP_LAUNCHER_OPEN_APP_BUTTON_LABEL);
       [self openExternalAppWithURL:URL prompt:prompt openLabel:openLabel];
       return YES;
     }
   }
 
   // Replaces |URL| with a rewritten URL if it is of mailto: scheme.
-  if (!experimental_flags::IsNativeAppLauncherEnabled() &&
-      gURL.SchemeIs(url::kMailToScheme)) {
+  if (gURL.SchemeIs(url::kMailToScheme)) {
     MailtoURLRewriter* rewriter =
         [[MailtoURLRewriter alloc] initWithStandardHandlers];
     NSString* launchURL = [rewriter rewriteMailtoURL:gURL];
     if (launchURL)
       URL = [NSURL URLWithString:launchURL];
     UMA_HISTOGRAM_BOOLEAN("IOS.MailtoURLRewritten", launchURL != nil);
   }
 
   // If the following call returns YES, an external application is about to be
   // launched and Chrome will go into the background now.
   // TODO(crbug.com/622735): This call still needs to be updated.
   // It's heavily nested so some refactoring is needed.
   return [[UIApplication sharedApplication] openURL:URL];
 }
 
 @end