Converted remoting.Error from an enum to a class

remoting/webapp/app_remoting/js/app_remoting.js

Index: remoting/webapp/app_remoting/js/app_remoting.js
diff --git a/remoting/webapp/app_remoting/js/app_remoting.js b/remoting/webapp/app_remoting/js/app_remoting.js
index 636b4200c03288d5cacfa07152b281b87004baad..8c1e6c51b6f8e690566dca11bc7bd2d1bc4f63ee 100644
--- a/remoting/webapp/app_remoting/js/app_remoting.js
+++ b/remoting/webapp/app_remoting/js/app_remoting.js
@@ -191,7 +191,7 @@ remoting.AppRemoting.prototype.init = function(connector) {
         that.runApplicationUrl(), parseAppHostResponse, '', headers);
   };
 
-  /** @param {remoting.Error} error */
+  /** @param {!remoting.Error} error */

[Jamie, 2015/02/26 18:57:42]

We haven't tended to be very rigourous about using ! in our types elsewhere. Do
you think there's much value in it?

[John Williams, 2015/02/27 21:42:11]

I'm a fan.  It catches some errors and I've never felt it caused a lot of extra
work (like "const poisoning" does).  And on the off chance you haven't
encountered it already, there's the esteemed C.A.R. Hoare:

I call it my billion-dollar mistake. It was the invention of the null reference
in 1965. At that time, I was designing the first comprehensive type system for
references in an object oriented language (ALGOL W). My goal was to ensure that
all use of references should be absolutely safe, with checking performed
automatically by the compiler. But I couldn't resist the temptation to put in a
null reference, simply because it was so easy to implement. This has led to
innumerable errors, vulnerabilities, and system crashes, which have probably
caused a billion dollars of pain and damage in the last forty years. In recent
years, a number of program analysers like PREfix and PREfast in Microsoft have
been used to check references, and give warnings if there is a risk they may be
non-null. More recent programming languages like Spec# have introduced
declarations for non-null references. This is the solution, which I rejected in
1965.

   var onError = function(error) {
     that.handleError(error);
   };
@@ -263,7 +263,7 @@ remoting.AppRemoting.prototype.handleDisconnected = function() {
  * Called when the current session's connection has failed.
  *
  * @param {remoting.SessionConnector} connector
- * @param {remoting.Error} error
+ * @param {!remoting.Error} error
  * @return {void} Nothing.
  */
 remoting.AppRemoting.prototype.handleConnectionFailed = function(
@@ -339,7 +339,7 @@ remoting.AppRemoting.prototype.handleExtensionMessage = function(
 /**
  * Called when an error needs to be displayed to the user.
  *
- * @param {remoting.Error} errorTag The error to be localized and displayed.
+ * @param {!remoting.Error} errorTag The error to be localized and displayed.
  * @return {void} Nothing.
  */
 remoting.AppRemoting.prototype.handleError = function(errorTag) {