Bug 963475 - Reverse the order of retrieval of message threads. r=gene

dom/mobilemessage/src/gonk/MobileMessageDB.jsm

@@ -2605,7 +2605,7 @@ MobileMessageDB.prototype = {
         if (DEBUG) debug("Caught error on transaction ", event.target.errorCode);
         collector.collect(null, COLLECT_ID_ERROR, COLLECT_TIMESTAMP_UNUSED);
       };
-      let request = threadStore.index("lastTimestamp").openKeyCursor();
+      let request = threadStore.index("lastTimestamp").openKeyCursor(null, PREV);
       request.onsuccess = function(event) {
         let cursor = event.target.result;
         if (cursor) {

dom/mobilemessage/tests/marionette/test_getthreads.js

@@ -376,6 +376,9 @@ checkFuncs.push(checkThread.bind(null, ["thread 18-1", "thread 18-2"],
 tasks.push(getAllThreads.bind(null, function(threads) {
   is(threads.length, checkFuncs.length, "number of threads got");
 
+  // Reverse threads as we iterate over them in reverse order
+  threads.reverse();
+
   (function callback() {
     if (!threads.length) {
       tasks.next();