[Cronet] Don't spam log if system cookie doesn't have creation time.

ios/BUILD.gn

 # Copyright 2016 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.
 
 assert(!is_component_build, "component build is unsupported on iOS")
 
+import("//ios/features.gni")
+
 declare_args() {
-  # Control whether cronet is build (this is usually set by the script
-  # components/cronet/tools/cr_cronet.py as cronet requires specific
-  # gn args to build correctly).
-  is_cronet_build = false
-
   # TODO(brettw) bug 684096: Remove these. These are to prevent unused
   # override warnings on iOS from the setting of the default_args in the
   # toplevel //.gn file. Since iOS doesn't compile V8, GN complains that
   # the overrides are never used.
   v8_extra_library_files = []
   v8_experimental_extra_library_files = []
   v8_enable_gdbjit = false
   v8_imminent_deprecation_warnings = false
 }
 
@@ skipping 33 matching lines @@
       "//ios/chrome/test/earl_grey:all_tests",
       "//ios/clean/chrome/test:all_tests",
       "//ios/net:all_tests",
       "//ios/showcase:all_tests",
       "//ios/testing:all_tests",
       "//ios/web:all_tests",
       "//ios/web/shell/test:all_tests",
     ]
   }
 }