Show all mailto: handlers, but dim unavailable ones.

ios/chrome/browser/web/mailto_url_rewriter.mm

 // Copyright 2017 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/mailto_url_rewriter.h"
 
 #import "base/logging.h"
 #import "ios/chrome/browser/web/mailto_handler.h"
 #import "ios/chrome/browser/web/mailto_handler_gmail.h"
 #import "ios/chrome/browser/web/mailto_handler_system_mail.h"
@@ skipping 95 matching lines @@
 - (NSString*)defaultHandlerName {
   NSString* handlerID = [self defaultHandlerID];
   MailtoHandler* handler = _handlers[handlerID];
   return [handler appName];
 }
 
 - (NSString*)rewriteMailtoURL:(const GURL&)gURL {
   NSString* value = [self defaultHandlerID];
   if ([value length]) {
     MailtoHandler* handler = _handlers[value];
-    if (handler) {
+    if ([handler isAvailable]) {
       return [handler rewriteMailtoURL:gURL];
     }
   }
   return nil;
 }
 
 #pragma mark - Private
 
 + (void)resetDefaultHandlerIDForTesting {
   [[NSUserDefaults standardUserDefaults]
       removeObjectForKey:kMailtoDefaultHandlerKey];
 }
 
 - (void)addMailtoApps:(NSArray<MailtoHandler*>*)handlerApps {
   for (MailtoHandler* app in handlerApps) {
-    if ([app isAvailable])
-      [_handlers setObject:app forKey:[app appStoreID]];
+    [_handlers setObject:app forKey:[app appStoreID]];
   }
   [self migrateLegacyOptions];
   [self autoDefaultToGmailIfInstalled];
 }
 
 //
 // Implements the migration logic for users of previous versions of Google
 // Chrome which supports Google Native App Launcher. The goal is to preserve
 // the previous behavior and support user choice of non-system provided Mail
 // client apps. System-provided Mail client app will be referred to as
@@ skipping 68 matching lines @@
   if ([defaults objectForKey:kMailtoDefaultHandlerKey])
     return;
 
   NSString* const kGmailAppStoreID = @"422689480";
   MailtoHandler* gmailHandler = _handlers[kGmailAppStoreID];
   if ([gmailHandler isAvailable])
     [defaults setObject:kGmailAppStoreID forKey:kMailtoDefaultHandlerKey];
 }
 
 @end