[CrOS Tether] Create TetherConnector, which attempts to connect to a nearby tether host.

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 18502af7c154f53b53e265f1c3a7bf696fc27aef..7474fa2347d2d4c743018e88e73bf010f4dbdb27 100644
--- a/chromeos/components/tether/BUILD.gn
+++ b/chromeos/components/tether/BUILD.gn
@@ -22,6 +22,8 @@ static_library("tether") {
     "ble_scanner.h",
     "connect_tethering_operation.cc",
     "connect_tethering_operation.h",
+    "device_id_tether_network_guid_map.cc",
+    "device_id_tether_network_guid_map.h",
     "host_scan_device_prioritizer.cc",
     "host_scan_device_prioritizer.h",
     "host_scan_scheduler.cc",
@@ -45,6 +47,8 @@ static_library("tether") {
     "notification_presenter.h",
     "pref_names.cc",
     "pref_names.h",
+    "tether_connector.cc",
+    "tether_connector.h",
     "tether_host_fetcher.cc",
     "tether_host_fetcher.h",
     "wifi_hotspot_connector.cc",
@@ -123,6 +127,7 @@ source_set("unit_tests") {
     "local_device_data_provider_unittest.cc",
     "message_transfer_operation_unittest.cc",
     "message_wrapper_unittest.cc",
+    "tether_connector_unittest.cc",
     "tether_host_fetcher_unittest.cc",
     "wifi_hotspot_connector_unittest.cc",
   ]