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" ]
-
-  # EarlGrey and its dependencies need to link to XCTest.framework
-  # that is not under $ios_sdk_path.
-  common_flags = [ "-F$ios_sdk_path/../../Library/Frameworks" ]
-  cflags_objc = common_flags
-  cflags_objcc = common_flags
-  ldflags = common_flags
 }
 
 ios_framework_bundle("earl_grey") {
   output_name = "EarlGrey"
   info_plist = "Info.plist"
 
   testonly = true
   sources = [
     "src/EarlGrey/Action/GREYAction.h",
     "src/EarlGrey/Action/GREYActionBlock.h",
@@ skipping 224 matching lines @@
 
   libs = [
     "CoreGraphics.framework",
     "Foundation.framework",
     "IOKit.framework",
     "QuartzCore.framework",
     "UIKit.framework",
     "XCTest.framework",
   ]
 
-  public_configs = [ ":config" ]
+  public_configs = [
+    ":config",
+    "//build/config/ios:xctest_config",
+  ]
+
   configs += [ "//build/config/compiler:enable_arc" ]
   configs -= [ "//build/config/gcc:symbol_visibility_hidden" ]
   configs += [ "//build/config/gcc:symbol_visibility_default" ]
 }