[Remoting Host] Handle text event characters that are not presented on the keyboard

remoting/host/BUILD.gn

Index: remoting/host/BUILD.gn
diff --git a/remoting/host/BUILD.gn b/remoting/host/BUILD.gn
index 51dcaada0d255950ed9239efd959c173e4aca11e..950593db447fa41116ab25bf2f180b7b45907775 100644
--- a/remoting/host/BUILD.gn
+++ b/remoting/host/BUILD.gn
@@ -208,6 +208,12 @@ static_library("host") {
     "linux/certificate_watcher.h",
     "linux/unicode_to_keysym.cc",
     "linux/unicode_to_keysym.h",
+    "linux/x11_character_injector.cc",
+    "linux/x11_character_injector.h",
+    "linux/x11_key_mapper.cc",
+    "linux/x11_key_mapper.h",
+    "linux/x11_keyboard_impl.cc",
+    "linux/x11_keyboard_impl.h",
     "linux/x11_util.cc",
     "linux/x11_util.h",
     "linux/x_server_clipboard.cc",
@@ -450,6 +456,8 @@ static_library("test_support") {
     "fake_oauth_token_getter.h",
     "host_mock_objects.cc",
     "host_mock_objects.h",
+    "linux/mock_x11_keyboard.cc",
+    "linux/mock_x11_keyboard.h",
     "setup/mock_oauth_client.cc",
     "setup/mock_oauth_client.h",
   ]
@@ -506,6 +514,7 @@ source_set("unit_tests") {
     "linux/audio_pipe_reader_unittest.cc",
     "linux/certificate_watcher_unittest.cc",
     "linux/unicode_to_keysym_unittest.cc",
+    "linux/x11_key_mapper_unittest.cc",
     "linux/x_server_clipboard_unittest.cc",
     "local_input_monitor_unittest.cc",
     "mouse_cursor_monitor_proxy_unittest.cc",