Remove Experimental Flag ExternalAppPromptDisabled

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/metrics/histogram_macros.h"
 #include "base/strings/sys_string_conversions.h"
@@ skipping 159 matching lines @@
                withObject:URL
                afterDelay:0.0];
     return YES;
   }
 
   // Don't open external application if chrome is not active.
   if ([[UIApplication sharedApplication] applicationState] !=
       UIApplicationStateActive)
     return NO;
 
-  if (experimental_flags::IsExternalApplicationPromptEnabled()) {
-    // Prompt user to open itunes when opening it is not a result of a link
-    // click.
-    if (!linkClicked && UrlHasAppStoreScheme(gURL)) {
-      [self performSelector:@selector(openExternalAppWithPromptForURL:)
-                 withObject:URL
-                 afterDelay:0.0];
-      return YES;
-    }
+  // Prompt user to open itunes when opening it is not a result of a link
+  // click.
+  if (!linkClicked && UrlHasAppStoreScheme(gURL)) {
+    [self performSelector:@selector(openExternalAppWithPromptForURL:)
+               withObject:URL
+               afterDelay:0.0];
+    return YES;
   }
 
   // Replaces |URL| with a rewritten URL if it is of mailto: scheme.
   if (!experimental_flags::IsNativeAppLauncherEnabled() &&
       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