Convert enable_one_click_signin to new buildflag system

chrome/test/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/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/chrome_tests.gni")
+import("//chrome/common/features.gni")
 import("//chrome/test/base/js2gtest.gni")
 import("//testing/test.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 # This target exists to reference other test executables to bring these files
 # into the build.
 group("test") {
@@ skipping 2207 matching lines @@
 if (is_android) {
   android_library("unit_tests_java") {
     DEPRECATED_java_in_dir = "//chrome/test/android/unit_tests_apk/src"
     deps = [
       "//base:base_java",
       "//chrome/android:chrome_java",
       "//content/public/android:content_java",
     ]
   }
 }