[Cronet] Disable DCHECK(created) in GetCreationTimeFromObject.

- iOS 12 returns nil for system cookie with null creation time.

Bug: 865803, 688540
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I612b4ab55aedb0a2c0d9b2a7cb24418c5a0a6c19
Reviewed-on: https://chromium-review.googlesource.com/1157229Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Misha Efimov <mef@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579763}

ios/net/cookies/cookie_creation_time_manager.mm

@@ -10,6 +10,7 @@
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/time/time.h"
+#include "ios/net/ios_net_buildflags.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
@@ -26,7 +27,11 @@ base::Time GetCreationTimeFromObject(NSHTTPCookie* cookie) {
   // The "Created" key is not documented.
   // Return a null time if the key is missing.
   id created = [[cookie properties] objectForKey:kHTTPCookieCreated];
+#if !BUILDFLAG(CRONET_BUILD)
+  // In Cronet the cookie store is recreated on startup, so |created| could be
+  // nil.
   DCHECK(created && [created isKindOfClass:[NSNumber class]]);
+#endif
   if (!created || ![created isKindOfClass:[NSNumber class]])
     return base::Time();
   // created is the time from January 1st, 2001 in seconds.