[CrOS Tether] Create TetherDisconnector, which disconnects from active tethering sessions.

chromeos/components/tether/BUILD.gn

Index: chromeos/components/tether/BUILD.gn
diff --git a/chromeos/components/tether/BUILD.gn b/chromeos/components/tether/BUILD.gn
index 882ddf21e26134d3a3515e96c7c35699216c358a..7adcb37424e4a191972c76330893adaa2dd5216e 100644
--- a/chromeos/components/tether/BUILD.gn
+++ b/chromeos/components/tether/BUILD.gn
@@ -50,11 +50,15 @@ static_library("tether") {
     "message_wrapper.h",
     "network_configuration_remover.cc",
     "network_configuration_remover.h",
+    "network_connection_handler_tether_delegate.cc",
+    "network_connection_handler_tether_delegate.h",
     "notification_presenter.h",
     "pref_names.cc",
     "pref_names.h",
     "tether_connector.cc",
     "tether_connector.h",
+    "tether_disconnector.cc",
+    "tether_disconnector.h",
     "tether_host_fetcher.cc",
     "tether_host_fetcher.h",
     "tether_host_response_recorder.cc",
@@ -94,6 +98,8 @@ static_library("test_support") {
     "fake_ble_connection_manager.h",
     "fake_host_scan_cache.cc",
     "fake_host_scan_cache.h",
+    "fake_network_configuration_remover.cc",
+    "fake_network_configuration_remover.h",
     "fake_notification_presenter.cc",
     "fake_notification_presenter.h",
     "fake_tether_host_fetcher.cc",
@@ -146,7 +152,9 @@ source_set("unit_tests") {
     "message_transfer_operation_unittest.cc",
     "message_wrapper_unittest.cc",
     "network_configuration_remover_unittest.cc",
+    "network_connection_handler_tether_delegate_unittest.cc",
     "tether_connector_unittest.cc",
+    "tether_disconnector_unittest.cc",
     "tether_host_fetcher_unittest.cc",
     "tether_host_response_recorder_unittest.cc",
     "tether_network_disconnection_handler_unittest.cc",