Remove content_settings_client.h abstraction which isn't used

chrome/browser/BUILD.gn

 # Copyright 2014 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/chrome_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/split_static_library.gni")
 import("//chrome/common/features.gni")
@@ skipping 228 matching lines @@
     "component_updater/sth_set_component_installer.cc",
     "component_updater/sth_set_component_installer.h",
     "component_updater/subresource_filter_component_installer.cc",
     "component_updater/subresource_filter_component_installer.h",
     "component_updater/supervised_user_whitelist_installer.cc",
     "component_updater/supervised_user_whitelist_installer.h",
     "component_updater/sw_reporter_installer_win.cc",
     "component_updater/sw_reporter_installer_win.h",
     "component_updater/swiftshader_component_installer.cc",
     "component_updater/swiftshader_component_installer.h",
-    "content_settings/chrome_content_settings_client.cc",
-    "content_settings/chrome_content_settings_client.h",
     "content_settings/chrome_content_settings_utils.cc",
     "content_settings/chrome_content_settings_utils.h",
     "content_settings/cookie_settings_factory.cc",
     "content_settings/cookie_settings_factory.h",
     "content_settings/host_content_settings_map_factory.cc",
     "content_settings/host_content_settings_map_factory.h",
     "content_settings/local_shared_objects_container.cc",
     "content_settings/local_shared_objects_container.h",
     "content_settings/tab_specific_content_settings.cc",
     "content_settings/tab_specific_content_settings.h",
@@ skipping 4011 matching lines @@
   # linking all of the test support.
   static_library("pepper_cdm_test_constants") {
     testonly = true
     visibility = [ "//chrome/*" ]
     sources = [
       "media/pepper_cdm_test_constants.cc",
       "media/pepper_cdm_test_constants.h",
     ]
   }
 }