Add chrome test support target to GN build.

chrome/app/BUILD.gn

 # Copyright 2014 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("//tools/grit/grit_rule.gni")
 
 # GYP version: chrome/chrome_resources.gyp:chrome_strings
 #              (generate_generated_resources action)
 grit("generated_resources") {
   source = "generated_resources.grd"
@@ skipping 203 matching lines @@
     "chromium_strings_ta.pak",
     "chromium_strings_te.pak",
     "chromium_strings_th.pak",
     "chromium_strings_tr.pak",
     "chromium_strings_uk.pak",
     "chromium_strings_vi.pak",
     "chromium_strings_zh-CN.pak",
     "chromium_strings_zh-TW.pak",
   ]
 }
+
+source_set("test_support") {
+  testonly = true
+  visibility = [ "//chrome/test:test_support" ]
+
+  sources = [
+    "chrome_main_delegate.cc",
+    "chrome_main_delegate.h",
+    "close_handle_hook_win.cc",
+    "close_handle_hook_win.h",
+  ]
+
+  deps = [
+    "//base",
+    "//chrome/browser",
+    "//chrome/common",
+    "//chrome/plugin",
+    "//chrome/renderer",
+    "//chrome/utility",
+    "//content/public/app:both",
+    "//content/public/common",
+    "//ui/base",
+  ]
+
+  if (is_mac) {
+    sources += [
+      "chrome_breakpad_client.cc",
+      "chrome_breakpad_client_mac.mm",
+      "chrome_main_mac.mm",
+    ]
+  }
+}