IME for Mus: Use ui::InputMethodChromeOS to provide logic for ime driver.

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index e39ee89ad082d4aeedc678b56710f07955169cdb..b389afe1e87833acbc311cedc6d119819888ccb1 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -4757,6 +4757,9 @@ test("unit_tests") {
       "../browser/ui/views/apps/app_info_dialog/app_info_permissions_panel_unittest.cc",
       "../browser/ui/views/website_settings/website_settings_popup_view_unittest.cc",
     ]
+    if (is_chromeos) {
+      sources += [ "../browser/ui/views/ime_driver/input_method_bridge_chromeos_unittest.cc" ]
+    }
     if (!is_chromeos && (!is_mac || mac_views_browser)) {
       sources += [
         "../browser/ui/views/frame/opaque_browser_frame_view_layout_unittest.cc",