Wire up an api to darken screen for accessibility

chrome/browser/chromeos/accessibility/accessibility_manager.cc

Index: chrome/browser/chromeos/accessibility/accessibility_manager.cc
diff --git a/chrome/browser/chromeos/accessibility/accessibility_manager.cc b/chrome/browser/chromeos/accessibility/accessibility_manager.cc
index 23b1832d56a59308d33986e8cf662ada86ec7e08..b90112b04441da6d23139508ca4bfc14f505e56b 100644
--- a/chrome/browser/chromeos/accessibility/accessibility_manager.cc
+++ b/chrome/browser/chromeos/accessibility/accessibility_manager.cc
@@ -58,6 +58,8 @@
 #include "chrome/grit/browser_resources.h"
 #include "chromeos/audio/audio_a11y_controller.h"
 #include "chromeos/audio/chromeos_sounds.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/power_manager_client.h"
 #include "components/prefs/pref_member.h"
 #include "components/prefs/pref_service.h"
 #include "content/public/browser/browser_accessibility_state.h"
@@ -1361,6 +1363,11 @@ void AccessibilityManager::PostUnloadChromeVox() {
     chromevox_panel_->Close();
     chromevox_panel_ = nullptr;
   }
+
+  // In case the user darkened the screen, undarken it now.
+  chromeos::DBusThreadManager::Get()
+      ->GetPowerManagerClient()
+      ->SetBacklightsForcedOff(false);
 }
 
 void AccessibilityManager::PostSwitchChromeVoxProfile() {