[ObjC ARC] Converts ios/chrome/browser/web:test_support to ARC.

ios/chrome/browser/web/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.
 
 import("//ios/web/js_compile.gni")
 
 source_set("web") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "dom_altering_lock.h",
@@ skipping 225 matching lines @@
     "//ios/web:user_agent",
     "//net",
     "//ui/base",
     "//ui/gfx",
     "//url",
   ]
   libs = [ "UIKit.framework" ]
 }
 
 source_set("test_support") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "chrome_web_test.h",
     "chrome_web_test.mm",
     "fake_mailto_handler_helpers.h",
     "fake_mailto_handler_helpers.mm",
   ]
   deps = [
     "//components/password_manager/core/browser:test_support",
     "//ios/chrome/browser/browser_state:test_support",
@@ skipping 90 matching lines @@
     "early_page_script_perftest.mm",
   ]
   deps = [
     "//base",
     "//ios/chrome/test/base:perf_test_support",
     "//ios/web",
     "//ios/web:test_support",
   ]
   libs = [ "WebKit.framework" ]
 }