Pass error messages from native messaging to web-app.

remoting/webapp/crd/js/host_daemon_facade.js

Index: remoting/webapp/crd/js/host_daemon_facade.js
diff --git a/remoting/webapp/crd/js/host_daemon_facade.js b/remoting/webapp/crd/js/host_daemon_facade.js
index 544abd39683d617c787e344caa5695f963b32a6a..cea917212dc8d0f342fc395b8d0a7b7b0260cf87 100644
--- a/remoting/webapp/crd/js/host_daemon_facade.js
+++ b/remoting/webapp/crd/js/host_daemon_facade.js
@@ -196,7 +196,13 @@ remoting.HostDaemonFacade.prototype.onIncomingMessage_ = function(message) {
   try {
     var type = base.getStringAttr(message, 'type');
     if (type != reply.type) {
-      throw 'Expected reply type: ' + reply.type + ', got: ' + type;
+      throw new Error('Expected reply type: ' + reply.type + ', got: ' + type);
+    }
+    var error_message = base.getStringAttr(message, 'error_message', '');
+    if (error_message) {
+      var error_location = base.getStringAttr(message, 'error_location',
+                                              '<unknown>')
+      console.error(error_message + ' at ' + error_location);
     }
     reply.deferred.resolve(message);
   } catch (/** @type {*} */ e) {