Convert some component source sets to static library

components/offline_pages/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.
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 # GYP: //components/offline_pages.gypi:offline_pages
 static_library("offline_pages") {
@@ skipping 51 matching lines @@
 
   deps = [
     ":offline_pages",
     ":switches",
     "//base",
     "//testing/gtest",
     "//url",
   ]
 }
 
-source_set("switches") {
+static_library("switches") {
   sources = [
     "offline_page_feature.cc",
     "offline_page_feature.h",
   ]
 
   deps = [
     "//base",
     "//components/version_info",
   ]
 }
@@ skipping 22 matching lines @@
   ]
 }
 
 if (is_android) {
   java_cpp_enum("offline_page_model_enums_java") {
     sources = [
       "offline_page_types.h",
     ]
   }
 }