Convert ios_web_shell_test to GN.

ios/web/shell/BUILD.gn

 # Copyright 2015 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")
 import("//ios/build/config.gni")
 
 ios_app_bundle("ios_web_shell") {
   info_plist = "Info.plist"
 
-  sources = [
-    "web_exe_main.mm",
-  ]
-
   deps = [
     ":shell",
 
     # All shared libraries must have the sanitizer deps to properly link in
     # asan mode (this target will be empty in other cases).
     "//build/config/sanitizers:deps",
   ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 
@@ skipping 24 matching lines @@
     "shell_network_delegate.cc",
     "shell_network_delegate.h",
     "shell_url_request_context_getter.h",
     "shell_url_request_context_getter.mm",
     "shell_web_client.h",
     "shell_web_client.mm",
     "shell_web_main_parts.h",
     "shell_web_main_parts.mm",
     "view_controller.h",
     "view_controller.mm",
+    "web_exe_main.mm",
   ]
 
   deps = [
     ":shell_bundle_data",
     "//base",
     "//ios/net",
     "//ios/web",
     "//ios/web:user_agent",
     "//ios/web/public/app",
     "//net",
     "//net:extras",
     "//ui/base",
   ]
 
   libs = [
     "CoreGraphics.framework",
     "CoreFoundation.framework",
     "Foundation.framework",
     "UIKit.framework",
   ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 }