Don't autostart Chromevox in tests when a braille display is connected.

chrome/browser/extensions/api/braille_display_private/stub_braille_controller.cc

Index: chrome/browser/extensions/api/braille_display_private/stub_braille_controller.cc
diff --git a/chrome/browser/extensions/api/braille_display_private/stub_braille_controller.cc b/chrome/browser/extensions/api/braille_display_private/stub_braille_controller.cc
index d1e0da830a1ad170d4bc3a0c4eb7ce5449091ac0..d1011f4b243643176fd8ac9c07a8bdbed89e9b2c 100644
--- a/chrome/browser/extensions/api/braille_display_private/stub_braille_controller.cc
+++ b/chrome/browser/extensions/api/braille_display_private/stub_braille_controller.cc
@@ -24,6 +24,12 @@ void StubBrailleController::AddObserver(BrailleObserver* observer) {
 void StubBrailleController::RemoveObserver(BrailleObserver* observer) {
 }
 
+StubBrailleController* StubBrailleController::GetInstance() {
+  return base::Singleton<
+      StubBrailleController,
+      base::LeakySingletonTraits<StubBrailleController>>::get();
+}
+
 }  // namespace braille_display_private
 }  // namespace api
 }  // namespace extensions