[Cronet] Add BUILD.gn for legacy ios/CrNet project.

ios/net/protocol_handler_util.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/net/protocol_handler_util.h"
 
 #include <string>
 
 #include "base/base64.h"
-#include "base/i18n/encoding_detection.h"
-#include "base/i18n/icu_string_conversions.h"
 #include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/time/time.h"
 #include "ios/net/crn_http_url_response.h"
 #import "net/base/mac/url_conversions.h"
 #include "net/base/net_errors.h"
 #include "net/http/http_request_headers.h"
 #include "net/http/http_response_headers.h"
 #include "net/http/http_version.h"
 #include "net/url_request/url_request.h"
 #include "url/gurl.h"
 #include "url/url_features.h"
 
+#if !BUILDFLAG(USE_PLATFORM_ICU_ALTERNATIVES)
+#include "base/i18n/encoding_detection.h"  // nogncheck
+#include "base/i18n/icu_string_conversions.h"  // nogncheck
+#endif  // !BUILDFLAG(USE_PLATFORM_ICU_ALTERNATIVES)
+
 namespace {
 
 // "Content-Type" HTTP header.
 NSString* const kContentType = @"Content-Type";
 
 }  // namespace
 
 namespace net {
 
 NSError* GetIOSError(NSInteger ns_error_code,
@@ skipping 173 matching lines @@
   if (out_request->has_upload() && out_request->method() == "POST") {
     DLOG_IF(WARNING, !net_headers.HasHeader(HttpRequestHeaders::kContentType))
         << "Missing \"Content-Type\" header in POST request.";
     net_headers.SetHeaderIfMissing(HttpRequestHeaders::kContentType,
                                    "application/x-www-form-urlencoded");
   }
   out_request->SetExtraRequestHeaders(net_headers);
 }
 
 }  // namespace net