Make TestRLZTrackerDelegate's SequencedWorkerPool multi-threaded.

components/rlz/rlz_tracker_unittest.cc

Index: components/rlz/rlz_tracker_unittest.cc
diff --git a/components/rlz/rlz_tracker_unittest.cc b/components/rlz/rlz_tracker_unittest.cc
index 5a37fe18b1d3909e59e5e080cf4afad53b940423..937bb4f7d8d0097110cb66a4226db69a0268f232 100644
--- a/components/rlz/rlz_tracker_unittest.cc
+++ b/components/rlz/rlz_tracker_unittest.cc
@@ -34,7 +34,7 @@ namespace {
 class TestRLZTrackerDelegate : public RLZTrackerDelegate {
  public:
   TestRLZTrackerDelegate()
-      : worker_pool_owner_(1, "TestRLZTracker"),
+      : worker_pool_owner_(2, "TestRLZTracker"),
         request_context_getter_(new net::TestURLRequestContextGetter(
             base::ThreadTaskRunnerHandle::Get())) {}