Migrate WaitableEvent to enum-based constructor in tools/

Change automated with clang-tidy (details @ https://crbug.com/612843#c13)

BUG=612843

Review-Url: https://codereview.chromium.org/2023003005
Cr-Original-Commit-Position: refs/heads/master@{#397225}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 3dbb1f62a6fbc115a027294b982db68d3d21012f

tools/gn/input_file_manager.cc

diff --git a/tools/gn/input_file_manager.cc b/tools/gn/input_file_manager.cc
index 36c0bf3..c695655 100644
--- a/tools/gn/input_file_manager.cc
+++ b/tools/gn/input_file_manager.cc
@@ -203,8 +203,11 @@
 
     if (!data->loaded) {
       // Wait for the already-pending sync load to complete.
-      if (!data->completion_event)
-        data->completion_event.reset(new base::WaitableEvent(false, false));
+      if (!data->completion_event) {
+        data->completion_event.reset(new base::WaitableEvent(
+            base::WaitableEvent::ResetPolicy::AUTOMATIC,
+            base::WaitableEvent::InitialState::NOT_SIGNALED));
+      }
       {
         base::AutoUnlock unlock(lock_);
         data->completion_event->Wait();