Convert ios_web_shell_test to GN.

ios/third_party/earl_grey/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/ios_sdk.gni")
 import("//build/config/ios/rules.gni")
 
 config("config") {
   include_dirs = [ "src/EarlGrey" ]
 
@@ skipping 245 matching lines @@
     "QuartzCore.framework",
     "UIKit.framework",
     "XCTest.framework",
   ]
 
   public_configs = [ ":config" ]
   configs += [ "//build/config/compiler:enable_arc" ]
   configs -= [ "//build/config/gcc:symbol_visibility_hidden" ]
   configs += [ "//build/config/gcc:symbol_visibility_default" ]
 }
+
+bundle_data("xctest_bundle") {
+  testonly = true
+
+  _ios_platform_library = "$ios_sdk_platform_path/Developer/Library"
+  sources = [
+    "$_ios_platform_library/Frameworks/XCTest.framework",

[justincohen, 2016/07/21 18:42:05]

Should this be a part of gn instead of earl grey?  If we ever add other xctests
that aren't earl grey, we will still need this.

[sdefresne, 2016/07/22 13:32:08]

Good idea, I've split the ios_eg_tests in two xctests and eg_tests (with
eg_tests just a wrapper around xctest that add dependencies on earl_grey).

+    "$_ios_platform_library/PrivateFrameworks/IDEBundleInjection.framework",
+  ]
+  outputs = [
+    "{{bundle_resources_dir}}/Frameworks/{{source_file_part}}",
+  ]
+}