Fix bug where DeterministicDispatcher CHECKed for killed jobs

headless/public/util/deterministic_dispatcher.h

Index: headless/public/util/deterministic_dispatcher.h
diff --git a/headless/public/util/deterministic_dispatcher.h b/headless/public/util/deterministic_dispatcher.h
index c2e73b6171084cef0a291821bc98b6b8223aa921..0fea383b9cc42e747b8daa65ad1ca3bf0193c649 100644
--- a/headless/public/util/deterministic_dispatcher.h
+++ b/headless/public/util/deterministic_dispatcher.h
@@ -10,6 +10,7 @@
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
 #include "headless/public/util/url_request_dispatcher.h"
@@ -54,6 +55,8 @@ class DeterministicDispatcher : public URLRequestDispatcher {
   // |io_thread_task_runner_|
   bool dispatch_pending_;
 
+  base::WeakPtrFactory<DeterministicDispatcher> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(DeterministicDispatcher);
 };