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

ios/chrome/browser/search_engines/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/features.gni")
+
+source_set("search_engines") {
+  sources = [
+    "search_engines_util.cc",
+    "search_engines_util.h",
+    "template_url_service_client_impl.cc",
+    "template_url_service_client_impl.h",
+    "template_url_service_factory.cc",
+    "template_url_service_factory.h",
+    "ui_thread_search_terms_data.cc",
+    "ui_thread_search_terms_data.h",
+  ]
+  deps = [
+    "//base",
+    "//components/google/core/browser",
+    "//components/history/core/browser",
+    "//components/keyed_service/core",
+    "//components/keyed_service/ios",
+    "//components/omnibox/browser",
+    "//components/prefs",
+    "//components/search",
+    "//components/search_engines",
+    "//components/version_info",
+    "//ios/chrome/browser:browser_no_public_deps",
+    "//ios/chrome/browser/browser_state",
+    "//ios/chrome/browser/google",
+    "//ios/chrome/browser/history",
+    "//ios/chrome/common",
+    "//ios/web",
+    "//net",
+    "//ui/base",
+    "//url",
+  ]
+
+  if (enable_rlz) {
+    deps += [ "//components/rlz" ]
+  }
+}