Migrate WaitableEvent to enum-based constructor in sync/

sync/internal_api/attachments/attachment_service_proxy_unittest.cc

Index: sync/internal_api/attachments/attachment_service_proxy_unittest.cc
diff --git a/sync/internal_api/attachments/attachment_service_proxy_unittest.cc b/sync/internal_api/attachments/attachment_service_proxy_unittest.cc
index 5c227c99ac9281364e93124277dfc62c8aa637d5..eb7b852265fe3b07cc0ece1188cfbc3df6af8864 100644
--- a/sync/internal_api/attachments/attachment_service_proxy_unittest.cc
+++ b/sync/internal_api/attachments/attachment_service_proxy_unittest.cc
@@ -113,7 +113,8 @@ class AttachmentServiceProxyTest : public testing::Test,
   }
 
   void WaitForStubThread() {
-    base::WaitableEvent done(false, false);
+    base::WaitableEvent done(base::WaitableEvent::ResetPolicy::AUTOMATIC,
+                             base::WaitableEvent::InitialState::NOT_SIGNALED);
     stub_thread->message_loop()->PostTask(
         FROM_HERE,
         base::Bind(&base::WaitableEvent::Signal, base::Unretained(&done)));