Makes sure the results are send /handled in right order

test/driver.js

@@ -232,10 +232,11 @@ function nextPage(task, loadError) {
   var failure = loadError || '';
 
   if (!task.pdfDoc) {
-    sendTaskResult(canvasToDataURL(), task, failure);
+    sendTaskResult(canvasToDataURL(), task, failure, function () {
       log('done' + (failure ? ' (failed !: ' + failure + ')' : '') + '\n');
       ++currentTaskIdx;
       nextTask();
+    });
     return;
   }
 
@@ -332,18 +333,12 @@ function nextPage(task, loadError) {
 function snapshotCurrentPage(task, failure) {
   log('done, snapshotting... ');
 
-  sendTaskResult(canvasToDataURL(), task, failure);
+  sendTaskResult(canvasToDataURL(), task, failure, function () {
     log('done' + (failure ? ' (failed !: ' + failure + ')' : '') + '\n');
 
-  // Set up the next request
-  var backoff = (inFlightRequests > 0) ? inFlightRequests * 10 : 0;
-  setTimeout(
-    function snapshotCurrentPageSetTimeout() {
     ++task.pageNum;
     nextPage(task);
-    },
+  });
-    backoff
-  );
 }
 
 function sendQuitRequest() {
@@ -373,10 +368,8 @@ function done() {
   }
 }
 
-function sendTaskResult(snapshot, task, failure, result) {
+function sendTaskResult(snapshot, task, failure, callback) {
-  // Optional result argument is for retrying XHR requests - see below
+  var result = JSON.stringify({
-  if (!result) {
-    result = JSON.stringify({
     browser: browser,
     id: task.id,
     numPages: task.pdfDoc ?
@@ -389,12 +382,11 @@ function sendTaskResult(snapshot, task, failure, result) {
     snapshot: snapshot,
     stats: task.stats.times
   });
-  }
 
-  send('/submit_task_results', result);
+  send('/submit_task_results', result, callback);
 }
 
-function send(url, message) {
+function send(url, message, callback) {
   var r = new XMLHttpRequest();
   // (The POST URI is ignored atm.)
   r.open('POST', url, true);
@@ -408,6 +400,9 @@ function send(url, message) {
           send(url, message);
         });
       }
+      if (callback) {
+        callback();
+      }
     }
   };
   document.getElementById('inFlightCount').innerHTML = inFlightRequests++;