[Continuation] Changed the GC::mark() method so as to get the current…

… timestamp for each marker. (Issue piece#4)

src/Piece/Flow/Continuation/GC.php

@@ -98,14 +98,13 @@ public function isMarked($pageFlowInstanceID)
      */
     public function mark()
     {
-        $thresholdTime = time();
         reset($this->markers);
         while (list($pageFlowInstanceID, $marker) = each($this->markers)) {
             if ($marker['swept']) {
                 continue;
             }
 
-            $this->markers[$pageFlowInstanceID]['shouldSweep'] = $thresholdTime - $marker['mtime'] > $this->expirationTime;
+            $this->markers[$pageFlowInstanceID]['shouldSweep'] = time() - $marker['mtime'] > $this->expirationTime;
         }
     }