Reduce chrome.exe .text size by 50 KB with static_library

components/variations/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.
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
-source_set("variations") {
+static_library("variations") {
   sources = [
     "active_field_trials.cc",
     "active_field_trials.h",
     "android/component_jni_registrar.cc",
     "android/component_jni_registrar.h",
     "android/variations_associated_data_android.cc",
     "android/variations_associated_data_android.h",
     "android/variations_seed_bridge.cc",
     "android/variations_seed_bridge.h",
     "caching_permuted_entropy_provider.cc",
@@ skipping 97 matching lines @@
   deps = [
     ":variations",
     "net",
     "proto",
     "//base/test:test_support",
     "//components/prefs:test_support",
     "//testing/gtest",
     "//third_party/zlib:compression_utils",
   ]
 }