Add trace to the caller of QuotaManager::GetAvailableSpace

storage/browser/quota/storage_monitor.cc

Index: storage/browser/quota/storage_monitor.cc
diff --git a/storage/browser/quota/storage_monitor.cc b/storage/browser/quota/storage_monitor.cc
index f312bd3c455e9e1c4d70efdd50eac96efe54b538..591cf538ffc7e9c0479c453a865c190c4d7f35e4 100644
--- a/storage/browser/quota/storage_monitor.cc
+++ b/storage/browser/quota/storage_monitor.cc
@@ -7,6 +7,7 @@
 #include <algorithm>
 
 #include "base/stl_util.h"
+#include "base/trace_event/trace_event.h"
 #include "net/base/net_util.h"
 #include "storage/browser/quota/quota_manager.h"
 #include "storage/common/quota/quota_status_code.h"
@@ -183,6 +184,8 @@ void HostStorageObservers::StartInitialization(
     const StorageObserver::Filter& filter) {
   if (initialized_ || initializing_)
     return;
+  // crbug.com/349708
+  TRACE_EVENT0("io", "HostStorageObservers::StartInitialization");
 
   initializing_ = true;
   quota_manager_->GetUsageAndQuotaForWebApps(