Convert some component source sets to static library

components/precache/core/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("//third_party/protobuf/proto_library.gni")
 
 # These values are duplicated in the GYP build in:
 # //components/precache/precache_defines.gypi
 precache_config_settings_url =
     "https://www.gstatic.com/chrome/wifiprefetch/precache_config"
 precache_manifest_url_prefix =
     "https://www.gstatic.com/chrome/wifiprefetch/hosts/"
 
 config("precache_config") {
   defines = [
     "PRECACHE_CONFIG_SETTINGS_URL=\"$precache_config_settings_url\"",
     "PRECACHE_MANIFEST_URL_PREFIX=\"$precache_manifest_url_prefix\"",
   ]
 }
 
-source_set("core") {
+static_library("core") {
   sources = [
     "fetcher_pool.h",
     "precache_database.cc",
     "precache_database.h",
     "precache_fetcher.cc",
     "precache_fetcher.h",
     "precache_session_table.cc",
     "precache_session_table.h",
     "precache_switches.cc",
     "precache_switches.h",
@@ skipping 42 matching lines @@
     ":proto",
     "//base",
     "//base/test:test_support",
     "//components/history/core/browser",
     "//net:test_support",
     "//sql",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }