[ObjC ARC] Converts ios/chrome/browser/net:eg_tests to ARC.

ios/chrome/browser/net/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.
 
 source_set("net") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "chrome_cookie_store_ios_client.h",
     "chrome_cookie_store_ios_client.mm",
     "connection_type_observer_bridge.h",
@@ skipping 61 matching lines @@
     "//base",
     "//base/test:test_support",
     "//ios/web:test_support",
     "//net",
     "//net:test_support",
     "//testing/gtest",
   ]
 }
 
 source_set("eg_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "cookies_egtest.mm",
   ]
   deps = [
     "//base",
     "//ios/chrome/test/app:test_support",
     "//ios/chrome/test/earl_grey:test_support",
     "//ios/third_party/earl_grey",
     "//ios/web:test_support",
     "//url",
   ]
   libs = [ "XCTest.framework" ]
 }