Retry w/ JSON to avoid cross-object contamination

test/driver.js

@@ -248,8 +248,11 @@ function done() {
   }
 }
 
-function sendTaskResult(snapshot, task, failure) {
-  var result = { browser: browser,
+function sendTaskResult(snapshot, task, failure, result) {
+  // Optional result argument is for retrying XHR requests - see below
+  if (!result) {
+    result = JSON.stringify({
+      browser: browser,
       id: task.id,
       numPages: task.pdfDoc ?
                (task.pageLimit || task.pdfDoc.numPages) : 0,
@@ -257,7 +260,9 @@ function sendTaskResult(snapshot, task, failure) {
       file: task.file,
       round: task.round,
       page: task.pageNum,
-                 snapshot: snapshot };
+      snapshot: snapshot
+    });
+  }
 
   var r = new XMLHttpRequest();
   // (The POST URI is ignored atm.)
@@ -268,11 +273,11 @@ function sendTaskResult(snapshot, task, failure) {
       inFlightRequests--;
       // Retry until successful
       if (r.status !== 200)
-        sendTaskResult(snapshot, task, failure);
+        sendTaskResult(null, null, null, result);
     }
   };
   document.getElementById('inFlightCount').innerHTML = inFlightRequests++;
-  r.send(JSON.stringify(result));
+  r.send(result);
 }
 
 function clear(ctx) {