Add the readonly restriction for output

Bug: 1019532
Change-Id: I9f1f9e23f27fd7771a03c10ca2deb733184b3a0b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1894534Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711762}

chrome/browser/resources/chromeos/chromevox/background/output.js

@@ -35,6 +35,7 @@ var DescriptionFromType = chrome.automation.DescriptionFromType;
 var Dir = constants.Dir;
 var EventType = chrome.automation.EventType;
 var NameFromType = chrome.automation.NameFromType;
+var Restriction = chrome.automation.Restriction;
 var RoleType = chrome.automation.RoleType;
 var StateType = chrome.automation.StateType;
 
@@ -343,8 +344,8 @@ Output.INPUT_TYPE_MESSAGE_IDS_ = {
  * @private
  */
 Output.RESTRICTION_STATE_MAP = {};
-Output.RESTRICTION_STATE_MAP[chrome.automation.Restriction.DISABLED] =
-    'aria_disabled_true';
+Output.RESTRICTION_STATE_MAP[Restriction.DISABLED] = 'aria_disabled_true';
+Output.RESTRICTION_STATE_MAP[Restriction.READ_ONLY] = 'aria_readonly_true';
 
 /**
  * Rules for mapping the checked property to a msg id