Use Message.OPEN_FEEDBACK_DIALOG instead of the string.

chrome://media-app uses a postMessage API to communicate between its trusted and
untrusted contexts to gain access to privileged functionality such as opening
the feedback dialog. Use an object (Message) to indicate the action being
communicated across the postMessage API instead of strings which are more error
prone.

Bug: 996088, b/138961540
Change-Id: I17185bdde143f8fb061ec2000075dd4a463cd7cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2096057
Commit-Queue: David Lei <dlei@google.com>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749025}

chromeos/components/media_app_ui/resources/js/launch.js

@@ -32,7 +32,7 @@ let currentlyWritableFileHandle = null;
 /** A pipe through which we can send messages to the guest frame. */
 const guestMessagePipe = new MessagePipe('chrome://media-app-guest');
 
-guestMessagePipe.registerHandler('openFeedbackDialog', () => {
+guestMessagePipe.registerHandler(Message.OPEN_FEEDBACK_DIALOG, () => {
   let response = media_app.handler.openFeedbackDialog();
   if (response === null) {
     response = {errorMessage: 'Null response received'};

chromeos/components/media_app_ui/resources/js/message_types.js

@@ -13,6 +13,7 @@
  */
 const Message = {
   LOAD_FILE: 'load-file',
+  OPEN_FEEDBACK_DIALOG: 'open-feedback-dialog',
   OVERWRITE_FILE: 'overwrite-file',
 };
 

chromeos/components/media_app_ui/resources/js/receiver.js

@@ -74,7 +74,8 @@ parentMessagePipe.registerHandler(Message.LOAD_FILE, (message) => {
 class Delegate {
   /** @override */
   async openFeedbackDialog() {
-    let response = await parentMessagePipe.sendMessage('openFeedbackDialog');
+    const response = await parentMessagePipe.sendMessage(
+      Message.OPEN_FEEDBACK_DIALOG);
     return /** @type {?string} */ (response['errorMessage']);
   }
 };