Use MessageSender.origin to check if sender is one of eligible clients.

When an extension message is received, we check `MessageSender.id` to
disallow requests from unknown clients.  Unfortunately,
`MessageSender.id` is currently not trustworthy (issue 982361) and
therefore this CL switches to using `MessageSender.origin` instead.

Bug: 10321587
Change-Id: I3729a407bef47e5ca4212ee3fe748b89c8d16a50
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031526Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737518}

ui/accessibility/extensions/chromevoxclassic/braille/braille_input_handler.js

@@ -89,12 +89,12 @@ cvox.BrailleInputHandler = function(translatorManager) {
 };
 
 /**
- * The ID of the Braille IME extension built into Chrome OS.
+ * The origin of the Braille IME extension built into Chrome OS.
  * @const {string}
  * @private
  */
-cvox.BrailleInputHandler.IME_EXTENSION_ID_ =
-    'jddehjeebkoimngcbdkaahpobgicbffp';
+cvox.BrailleInputHandler.IME_EXTENSION_ORIGIN_ =
+    'chrome-extension://jddehjeebkoimngcbdkaahpobgicbffp';
 
 /**
  * Name of the port to use for communicating with the Braille IME.
@@ -331,7 +331,7 @@ cvox.BrailleInputHandler.prototype = {
    */
   onImeConnect_: function(port) {
     if (port.name !== cvox.BrailleInputHandler.IME_PORT_NAME_ ||
-        port.sender.id !== cvox.BrailleInputHandler.IME_EXTENSION_ID_) {
+        port.sender.origin !== cvox.BrailleInputHandler.IME_EXTENSION_ORIGIN_) {
       return;
     }
     if (this.imePort_)