Split //ios/chrome/browser in multiple targets.

ios/chrome/browser/variations/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("//components/variations/service/generate_ui_string_overrider.gni")
 
+source_set("variations") {
+  sources = [
+    "ios_chrome_variations_service_client.cc",
+    "ios_chrome_variations_service_client.h",
+  ]
+  deps = [
+    "//base",
+    "//components/variations/service",
+    "//components/version_info",
+    "//ios/chrome/browser:browser_no_public_deps",
+    "//ios/chrome/common",
+    "//ios/web",
+  ]
+}
+
 generate_ui_string_overrider("ios_chrome_ui_string_overrider_factory") {
   inputs = [
     "$root_gen_dir/components/strings/grit/components_chromium_strings.h",
     "$root_gen_dir/components/strings/grit/components_google_chrome_strings.h",
     "$root_gen_dir/components/strings/grit/components_locale_settings.h",
     "$root_gen_dir/components/strings/grit/components_strings.h",
     "$root_gen_dir/ios/chrome/grit/ios_chromium_strings.h",
     "$root_gen_dir/ios/chrome/grit/ios_google_chrome_strings.h",
     "$root_gen_dir/ios/chrome/grit/ios_strings.h",
   ]
   deps = [
     "//components/strings:components_chromium_strings",
     "//components/strings:components_google_chrome_strings",
     "//components/strings:components_locale_settings",
     "//components/strings:components_strings",
     "//ios/chrome/app/strings:ios_chromium_strings",
     "//ios/chrome/app/strings:ios_google_chrome_strings",
     "//ios/chrome/app/strings:ios_strings",
   ]
   namespace = ""  # Put the functions in the global namespace on iOS.
   header_filename = "ios_ui_string_overrider_factory.h"
   source_filename = "ios_ui_string_overrider_factory.cc"
 }