Introduce the ThrottleManager

components/subresource_filter/content/browser/BUILD.gn

 # Copyright 2016 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.
 
 static_library("browser") {
   sources = [
     "activation_state_computing_navigation_throttle.cc",
     "activation_state_computing_navigation_throttle.h",
     "async_document_subresource_filter.cc",
     "async_document_subresource_filter.h",
     "content_ruleset_service_delegate.cc",
     "content_ruleset_service_delegate.h",
     "content_subresource_filter_driver_factory.cc",
     "content_subresource_filter_driver_factory.h",
+    "content_subresource_filter_throttle_manager.cc",
+    "content_subresource_filter_throttle_manager.h",
     "subframe_navigation_filtering_throttle.cc",
     "subframe_navigation_filtering_throttle.h",
     "subresource_filter_client.h",
     "verified_ruleset_dealer.cc",
     "verified_ruleset_dealer.h",
   ]
   deps = [
     "//base",
     "//components/safe_browsing_db:util",
     "//components/subresource_filter/content/common",
     "//components/subresource_filter/core/browser",
     "//components/subresource_filter/core/common",
     "//content/public/browser",
     "//content/public/common",
     "//ipc",
     "//net",
     "//url",
   ]
   public_deps = [
     "//ui/base",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "async_document_subresource_filter_unittest.cc",
     "content_ruleset_service_delegate_unittest.cc",
     "content_subresource_filter_driver_factory_unittest.cc",
+    "content_subresource_filter_throttle_manager_unittest.cc",
     "subframe_navigation_filtering_throttle_unittest.cc",
     "verified_ruleset_dealer_unittest.cc",
   ]
   deps = [
     ":browser",
     "//base/test:test_support",
     "//components/safe_browsing_db:util",
     "//components/subresource_filter/content/common",
     "//components/subresource_filter/core/browser",
     "//components/subresource_filter/core/browser:test_support",
     "//components/subresource_filter/core/common",
     "//components/subresource_filter/core/common:test_support",
     "//content/test:test_support",
     "//ipc",
     "//ipc:test_support",
     "//testing/gtest",
   ]
 }