Send messages using SockJS on staging

(imported from commit 812d20b1eab76eeb0d8fb92029fdb38d5faa9cce)

static/js/compose.js

@@ -315,6 +315,36 @@ function compose_error(error_text, bad_input) {
 
 var send_options;
 
+function send_message_ajax(request, success) {
+    $.ajax({
+        dataType: 'json', // This seems to be ignored. We still get back an xhr.
+        url: '/json/send_message',
+        type: 'POST',
+        data: request,
+        success: success,
+        error: function (xhr, error_type) {
+            if (error_type !== 'timeout' && reload.is_pending()) {
+                // The error might be due to the server changing
+                reload.initiate({immediate: true, send_after_reload: true});
+                return;
+            }
+            var response = util.xhr_error_message("Error sending message", xhr);
+            compose_error(response, $('#new_message_content'));
+        }
+    });
+}
+
+var socket = new Socket("/sockjs");
+function send_message_socket(request, success) {
+    socket.send(request, success, function (type, resp) {
+        var err_msg = "Error sending message";
+        if (type === 'response') {
+            err_msg += ": " + resp.msg;
+        }
+        compose_error(err_msg, $('#new_message_content'));
+    });
+}
+
 function send_message() {
     var request = create_message_object();
     exports.snapshot_message(request);
@@ -325,12 +355,7 @@ function send_message() {
         request.to = JSON.stringify([request.to]);
     }
 
-    $.ajax({
+    function success() {
-        dataType: 'json', // This seems to be ignored. We still get back an xhr.
-        url: '/json/send_message',
-        type: 'POST',
-        data: request,
-        success: function (resp, statusText, xhr) {
         $("#new_message_content").val('').focus();
         autosize_textarea();
         $("#send-status").hide(0);
@@ -342,18 +367,13 @@ function send_message() {
         clear_message_snapshot();
         $("#compose-send-button").removeAttr('disabled');
         $("#sending-indicator").hide();
-        },
-        error: function (xhr, error_type) {
-            if (error_type !== 'timeout' && reload.is_pending()) {
-                // The error might be due to the server changing
-                reload.initiate({immediate: true, send_after_reload: true});
-                return;
     }
-            var response = util.xhr_error_message("Error sending message", xhr);
-            compose_error(response, $('#new_message_content'));
-        }
-    });
 
+    if (feature_flags.use_socket) {
+        send_message_socket(request, success);
+    } else {
+        send_message_ajax(request, success);
+    }
 }
 
 exports.finish = function () {

static/js/feature_flags.js

@@ -35,6 +35,7 @@ exports.left_side_userlist = page_params.staging ||
 
 // Still very beta:
 exports.fade_users_when_composing = page_params.staging || is_customer4;
+exports.use_socket = page_params.staging;
 
 
 // Still burning in...