Split //ios/chrome/browser/prefs to prevent circular dependencies.

ios/chrome/test/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("//ios/build/config.gni")
 import("//ios/public/provider/chrome/browser/build_config.gni")
 import("//testing/test.gni")
 
 group("all_tests") {
   testonly = true
@@ skipping 18 matching lines @@
   ]
 
   deps = [
     "//base",
     "//components/content_settings/core/common",
     "//components/network_time",
     "//components/prefs",
     "//components/prefs:test_support",
     "//ios/chrome/browser",
     "//ios/chrome/browser/browser_state:browser_state_impl",
-    "//ios/chrome/browser/prefs",
+    "//ios/chrome/browser/prefs:browser_prefs",
     "//ios/public/provider/chrome/browser",
     "//ios/public/provider/chrome/browser:test_support",
     "//ios/web",
     "//ios/web:test_support",
     "//net",
     "//testing/gmock",
     "//testing/gtest",
     "//ui/base",
     "//url",
   ]
@@ skipping 64 matching lines @@
     "//ios/chrome/browser/voice:unit_tests",
     "//ios/chrome/browser/web:unit_tests",
     "//ios/chrome/browser/web_resource:unit_tests",
     "//ios/chrome/common:unit_tests",
     "//ios/chrome/test/base:unit_tests",
     "//ios/web/public/image_fetcher:unit_tests",
   ]
 
   assert_no_deps = ios_assert_no_deps
 }