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

ios/chrome/browser/ui/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("//build/config/ios/rules.gni")
 
 source_set("ui") {
   sources = [
     "UIView+SizeClassSupport.h",
     "UIView+SizeClassSupport.mm",
@@ skipping 331 matching lines @@
     "PassKit.framework",
     "Photos.framework",
     "QuartzCore.framework",
     "StoreKit.framework",
     "UIKit.framework",
     "WebKit.framework",
   ]
 }
 
 source_set("test_support") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "browser_view_controller_testing.h",
     "browser_view_controller_testing.mm",
   ]
   deps = [
     ":ui_internal",
     "//ios/chrome/browser/ui/toolbar",
     "//ios/chrome/browser/ui/toolbar:test_support",
   ]
@@ skipping 67 matching lines @@
     "//ios/chrome/test/base:perf_test_support",
     "//ios/shared/chrome/browser/tabs",
     "//ios/shared/chrome/browser/tabs:test_support",
     "//ios/web:test_support",
     "//testing/gtest",
     "//third_party/ocmock",
     "//ui/base:test_support",
   ]
   libs = [ "UIKit.framework" ]
 }