Added unit tests for switch_access.js.

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index 99b55d39b6a79a9ff654bf5e4c37b5de955e4bc1..18533186a5fe24ae43c00d4b4202b74d4efef138 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -3037,11 +3037,15 @@ js2gtest("unit_tests_js") {
     sources += [
       "../browser/resources/chromeos/braille_ime/braille_ime_unittest.gtestjs",
       "../browser/resources/chromeos/select_to_speak/select_to_speak_unittest.gtestjs",
+      "../browser/resources/chromeos/switch_access/switch_access_unittest.gtestjs",
     ]
     extra_js_files += [
       "../browser/resources/chromeos/braille_ime/braille_ime.js",
       "../browser/resources/chromeos/select_to_speak/select_to_speak.js",
       "../browser/resources/chromeos/select_to_speak/test_support.js",
+      "../browser/resources/chromeos/switch_access/switch_access.js",
+      "../browser/resources/chromeos/switch_access/test_support.js",
+      "../browser/resources/chromeos/switch_access/testable_switch_access.js",
     ]
   }
 }