Add beforeUnload handler to confirm exit.

remoting/webapp/me2mom/_locales/en/messages.json

 {
   "accessCode": {
     "message": "Access code",
     "description": "Label for the access code entry box"
   },
   "accessCodeTimer": {
     "message": "This access code will expire in",
     "description": "Text preceding the access code timer"
   },
   "cancel": {
     "message": "Cancel",
     "description": "Label for general-purpose Cancel buttons"
   },
+  "closePromptClient": {
+    "message": "Navigating away from this page will end your Chromoting session.",
+    "description": "Message shown when the client tab is closed while a connection is active."
+  },
+  "closePromptHost": {
+    "message": "Navigating away from this page will disconnect the Chromoting viewer.",
+    "description": "Message shown when the host tab is closed while a connection is active."
+  },
   "connectButton": {
     "message": "Connect",
     "description": "Label for the connect button"
   },
   "continueButton": {
     "message": "Continue",
     "description": "Label for the continue button on the pre-authorization page"
   },
   "debugButton": {
     "message": "Debug Log",
@@ skipping 143 matching lines @@
   },
   "webappDescription": {
     "message": "IT2Me-style remote support in Chrome.",
     "description": "Web-app description"
   },
   "webappName": {
     "message": "Remoting IT2Me",
     "description": "Web-app name"
   }
 }