[Easy Unlock] Port the BluetoothThrottler class to native code.

components/proximity_auth/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.
 
 source_set("proximity_auth") {
   sources = [
     "base64url.cc",
     "base64url.h",
     "bluetooth_connection.cc",
     "bluetooth_connection.h",
     "bluetooth_connection_finder.cc",
     "bluetooth_connection_finder.h",
+    "bluetooth_throttler.cc",
+    "bluetooth_throttler.h",
     "bluetooth_util.cc",
     "bluetooth_util_chromeos.cc",
     "bluetooth_util.h",
     "client.cc",
     "client.h",
     "client_observer.h",
     "connection.cc",
     "connection.h",
     "connection_finder.h",
     "connection_observer.h",
@@ skipping 13 matching lines @@
     "//net",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "base64url_unittest.cc",
     "bluetooth_connection_unittest.cc",
     "bluetooth_connection_finder_unittest.cc",
+    "bluetooth_throttler_unittest.cc",
     "client_unittest.cc",
     "connection_unittest.cc",
     "proximity_auth_system_unittest.cc",
     "remote_status_update_unittest.cc",
     "wire_message_unittest.cc",
   ]
 
   deps = [
     ":proximity_auth",
     "cryptauth:unit_tests",
     "//base/test:test_support",
     "//device/bluetooth:mocks",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }
 
 # Note: This is a convenience target for ease of rapid iteration during
 # development. It is not executed on any try or build bots.
 test("proximity_auth_unittests") {
   sources = [ "run_all_unittests.cc" ]
   deps = [ ":unit_tests" ]
 }