Merge pull request #1721 from ether/dont-send-same-cs-spam

temp patch for #1652

src/static/js/Changeset.js

@@ -1663,9 +1663,16 @@ exports.appendATextToAssembler = function (atext, assem) {
  * @param cs {Changeset} 
  * @param pool {AtributePool}
  */
+var lastEvent = null; // This is just a temporary measure to ensure we don't send the exact same changeset twice
+// Documentation for this is available at https://github.com/ether/etherpad-lite/issues/1652
+
 exports.prepareForWire = function (cs, pool) {
+  if(cs == lastEvent){
+    throw new Error("Not sending the same event twice...");
+  }
   var newPool = new AttributePool();
   var newCs = exports.moveOpsToNewPool(cs, pool, newPool);
+  lastEvent = cs;
   return {
     translated: newCs,
     pool: newPool