Show a helpful error message if a host domain policy blocked an attempt to use

remoting/webapp/_locales/en/messages.json

 {
   "ACCESS_CODE": {
     "message": "Access code",
     "description": "Label for the access code entry box. This is where the client user enters the code that permits access to the host."
   },
   "ACCESS_CODE_TIMER": {
     "message": "This access code will expire in $timeout$",
     "description": "Text displayed when the access code is due to time out within 30 seconds.",
     "placeholders": {
       "timeout": {
@@ skipping 132 matching lines @@
     "description": "Error that is shown on the client side when we don't get a response from the host."
   },
   "ERROR_INCOMPATIBLE_PROTOCOL": {
     "message": "An incompatible version of Chromoting was detected. Please make sure that you have the latest version of Chromium and Chromoting on both computers and try again.",
     "description": "Error that is shown on the client side when incompatible Chromoting versions are installed on host and client."
   },
   "ERROR_INVALID_ACCESS_CODE": {
     "message": "The access code is invalid. Please try again.",
     "description": "Error displayed if an invalid access code is entered."
   },
+  "ERROR_INVALID_HOST_DOMAIN": {
+    "message": "This computer does not let you use it as a Chromoting host.",

[Jamie, 2012/09/19 17:37:59]

For the NAT traversal warning, we specifically refer to policy settings. I think
we should do the same here. Perhaps "Policy settings do not permit sharing this
computer as a Chromoting host." Since we try to include a remedy in such
situations, I'd suggest "Contact your system administrator for assistance." as
well.

[simonmorris, 2012/09/19 18:01:02]

Done.

+    "description": "Error displayed when the computer has a policy that only users in a particular domain may use it as a Chromoting host, and a user in a different domain is trying to use it as a Chromoting host."
+  },
   "ERROR_NETWORK_FAILURE": {
     "message": "Unable to reach the host. This is probably due to the configuration of the network you are using.",
     "description": "Error displayed when the host is online, but we are unable to connect to it due to network configuration."
   },
   "ERROR_NOT_AUTHENTICATED": {
     "message": "You are not signed in to Chromoting. Please sign in and try again.",
     "description": "Error displayed when an operation is attempted that requires a signed-in user, but no-one is currently signed in."
   },
   "ERROR_MISSING_PLUGIN": {
     "message": "Some components required for Chromoting are missing. Please make sure you're running the latest version of Chromium and try again.",
@@ skipping 331 matching lines @@
   },
   "WARNING_NAT_DISABLED": {
     "message": "NOTE: Policy settings permit connections only between computers within your network.",
     "description": "Message displayed at the bottom of the host screen if local policy dictates that NAT traversal is disabled, meaning that connections outside the local network will not work."
   },
   "WHY_IS_THIS_SAFE": {
     "message": "Why is this safe?",
     "description": "Help link displayed when the user enables the host on this computer. Clicking this link opens a page that explains why this operation is safe. This string appears in a UI with limited horizontal space. Please try to keep translations no more than about 30 characters."
   }
 }