Refactor SecurityStateModel/Clients for simplicity and reusability.

components/security_state/core/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/config.gni")
   import("//build/config/android/rules.gni")
 }
 
-static_library("security_state") {
+static_library("core") {
   sources = [
     "security_state_model.cc",
     "security_state_model.h",
-    "security_state_model_client.h",
     "switches.cc",
     "switches.h",
   ]
 
   deps = [
     "//base",
     "//net",
   ]
 }
 
 if (is_android) {
   java_cpp_enum("security_state_enums_java") {
     sources = [
       "security_state_model.h",
     ]
   }
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "security_state_model_unittest.cc",
   ]
 
   deps = [
-    ":security_state",
+    ":core",
     "//net:test_support",
     "//testing/gtest",
   ]
 }