Migrate WaitableEvent to enum-based constructor in completion_event.h

cc/base/completion_event.h

Index: cc/base/completion_event.h
diff --git a/cc/base/completion_event.h b/cc/base/completion_event.h
index 36e8954c99565f35b70847b1cc3b85cdbc1b8667..edee0b78bf0e7bff28b07b878faae6a2ea858cce 100644
--- a/cc/base/completion_event.h
+++ b/cc/base/completion_event.h
@@ -19,7 +19,8 @@ namespace cc {
 class CompletionEvent {
  public:
   CompletionEvent()
-      : event_(false /* manual_reset */, false /* initially_signaled */) {
+      : event_(base::WaitableEvent::ResetPolicy::AUTOMATIC,
+               base::WaitableEvent::InitialState::NOT_SIGNALED) {
 #if DCHECK_IS_ON()
     waited_ = false;
     signaled_ = false;