Add QuicFlagUtils to quic/platform. No behavior change.

net/BUILD.gn

 # Copyright (c) 2013 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("//build/buildflag_header.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
@@ skipping 1309 matching lines @@
       "quic/core/quic_write_blocked_list.cc",
       "quic/core/quic_write_blocked_list.h",
       "quic/core/spdy_utils.cc",
       "quic/core/spdy_utils.h",
       "quic/platform/api/quic_aligned.h",
       "quic/platform/api/quic_bug_tracker.h",
       "quic/platform/api/quic_clock.cc",
       "quic/platform/api/quic_clock.h",
       "quic/platform/api/quic_containers.h",
       "quic/platform/api/quic_export.h",
+      "quic/platform/api/quic_flag_utils.h",
       "quic/platform/api/quic_hostname_utils.cc",
       "quic/platform/api/quic_hostname_utils.h",
       "quic/platform/api/quic_ip_address.cc",
       "quic/platform/api/quic_ip_address.h",
       "quic/platform/api/quic_ip_address_family.h",
       "quic/platform/api/quic_logging.h",
       "quic/platform/api/quic_lru_cache.h",
       "quic/platform/api/quic_map_util.h",
       "quic/platform/api/quic_mutex.cc",
       "quic/platform/api/quic_mutex.h",
       "quic/platform/api/quic_ptr_util.h",
       "quic/platform/api/quic_reference_counted.h",
       "quic/platform/api/quic_socket_address.cc",
       "quic/platform/api/quic_socket_address.h",
       "quic/platform/api/quic_stack_trace.h",
       "quic/platform/api/quic_str_cat.h",
       "quic/platform/api/quic_text_utils.h",
       "quic/platform/api/quic_url.cc",
       "quic/platform/api/quic_url.h",
       "quic/platform/api/quic_url_utils.cc",
       "quic/platform/api/quic_url_utils.h",
       "quic/platform/impl/quic_aligned_impl.h",
       "quic/platform/impl/quic_bug_tracker_impl.h",
       "quic/platform/impl/quic_chromium_clock.cc",
       "quic/platform/impl/quic_chromium_clock.h",
       "quic/platform/impl/quic_containers_impl.h",
       "quic/platform/impl/quic_export_impl.h",
+      "quic/platform/impl/quic_flag_utils_impl.h",
       "quic/platform/impl/quic_hostname_utils_impl.cc",
       "quic/platform/impl/quic_hostname_utils_impl.h",
       "quic/platform/impl/quic_ip_address_impl.cc",
       "quic/platform/impl/quic_ip_address_impl.h",
       "quic/platform/impl/quic_logging_impl.h",
       "quic/platform/impl/quic_lru_cache_impl.h",
       "quic/platform/impl/quic_map_util_impl.h",
       "quic/platform/impl/quic_mutex_impl.cc",
       "quic/platform/impl/quic_mutex_impl.h",
       "quic/platform/impl/quic_ptr_util_impl.h",
@@ skipping 4365 matching lines @@
       "tools/transport_security_state_generator/trie/trie_writer.cc",
       "tools/transport_security_state_generator/trie/trie_writer.h",
     ]
     deps = [
       "//base",
       "//crypto",
       "//third_party/boringssl",
     ]
   }
 }