Ensure invalid message ids are not read

Some roles e.g. ignored (found copiously in Android apps) are never meant to be localized. This also enforces a valid message id for any given string and makes it obvious when coming across a missing msg id.

Bug: 934512:
Test: manual
Change-Id: I6ac9650df4f3617836feef3999bfef6d1d58e449
Reviewed-on: https://chromium-review.googlesource.com/c/1478948
Commit-Queue: David Tseng <dtseng@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634474}

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

@@ -1436,9 +1436,9 @@ Output.prototype = {
             else
               msg = Msgs.getMsg(info.msgId);
           } else {
-            var errorMsg = 'Missing role info for ' + node.role;
-            ruleStr.writeError(errorMsg);
-            console.error(errorMsg);
+            // We can safely ignore this role. ChromeVox output tests cover
+            // message id validity.
+            return;
           }
           this.append_(buff, msg || '', options);
           ruleStr.writeTokenWithValue(token, msg);