[iOS] Fix ios_web_shell to build with 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")
 
 app("ios_web_shell") {
   info_plist = "Info.plist"
   entitlements_path = ""
   code_signing_identity = ""
 
   sources = [
     "web_exe_main.mm",
   ]
 
   deps = [
     ":shell",
   ]
 
   ldflags = [
     "-Xlinker",
     "-objc_abi_version",
     "-Xlinker",
     "2",
   ]
+}
 
-  # TODO(crbug.com/546283): once gn supports bundle resources, add support for
-  # the following gyp code:
-  #
-  # 'mac_bundle_resources': [
-  #   'shell/Default.png',
-  #   'shell/MainView.xib',
-  #   'shell/textfield_background@2x.png',
-  #   'shell/toolbar_back@2x.png',
-  #   'shell/toolbar_forward@2x.png',
-  # ],
+bundle_data_xib("main_view_bundle_data") {
+  visibility = [ ":shell" ]
+  source = "MainView.xib"
+}
+
+bundle_data("shell_bundle_data") {
+  visibility = [ ":shell" ]
+  sources = [
+    "Default.png",
+    "textfield_background@2x.png",
+    "toolbar_back@2x.png",
+    "toolbar_forward@2x.png",
+  ]
+  outputs = [
+    "{{bundle_resources_dir}}/{{source_file_part}}",
+  ]
 }
 
 source_set("shell") {
   sources = [
     "app_delegate.h",
     "app_delegate.mm",
     "shell_browser_state.h",
     "shell_browser_state.mm",
     "shell_main_delegate.h",
     "shell_main_delegate.mm",
     "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",
   ]
 
   deps = [
+    ":main_view_bundle_data",
+    ":shell_bundle_data",
     "//base",
     "//ios/web",
     "//ios/web/public/app",
     "//net",
     "//net:extras",
     "//ui/base",
 
     # 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",
   ]
 
   libs = [
     "CoreGraphics.framework",
     "CoreFoundation.framework",
     "Foundation.framework",
     "UIKit.framework",
   ]
 }