Wire up an api to darken screen for accessibility

chrome/browser/resources/chromeos/chromevox/cvox2/background/command_handler.js

Index: chrome/browser/resources/chromeos/chromevox/cvox2/background/command_handler.js
diff --git a/chrome/browser/resources/chromeos/chromevox/cvox2/background/command_handler.js b/chrome/browser/resources/chromeos/chromevox/cvox2/background/command_handler.js
index f37c37318f0dc822ea013835bc0c7c5e487a6a26..bb5839053c207cc0da9379d9a5d02db9d55b16d8 100644
--- a/chrome/browser/resources/chromeos/chromevox/cvox2/background/command_handler.js
+++ b/chrome/browser/resources/chromeos/chromevox/cvox2/background/command_handler.js
@@ -192,6 +192,20 @@ CommandHandler.onCommand = function(command) {
     case 'showNextUpdatePage':
       (new PanelCommand(PanelCommandType.UPDATE_NOTES)).send();
       return false;
+    case 'darkenScreen':
+      chrome.automation.getDesktop(function(desktop) {
+        desktop.toggleDarkenScreen(false);

[dmazzoni, 2017/03/22 21:40:48]

Why call it twice?

[David Tseng, 2017/03/22 22:51:38]

The other end of the dbus message is sticky. So, if you turned backlights off in
the past and adjusted brightness, the force backlights flag is still off, but
the screen is on. To get back to a known state, we need to clear the previous
state.

+        desktop.toggleDarkenScreen(true);
+      });
+      new Output().format('@darken_screen').go();
+      break;
+    case 'undarkenScreen':
+      chrome.automation.getDesktop(function(desktop) {
+        desktop.toggleDarkenScreen(true);
+        desktop.toggleDarkenScreen(false);
+      });
+      new Output().format('@undarken_screen').go();
+      break;
     default:
       break;
   }