Add trace to the caller of QuotaManager::GetAvailableSpace

chrome/browser/sync_file_system/local/canned_syncable_file_system.cc

Index: chrome/browser/sync_file_system/local/canned_syncable_file_system.cc
diff --git a/chrome/browser/sync_file_system/local/canned_syncable_file_system.cc b/chrome/browser/sync_file_system/local/canned_syncable_file_system.cc
index 9eb24c74e0444e09d76c406ba146497c6fdd75b6..ab18150f2a62594fc998e0bff44c93231e0927c6 100644
--- a/chrome/browser/sync_file_system/local/canned_syncable_file_system.cc
+++ b/chrome/browser/sync_file_system/local/canned_syncable_file_system.cc
@@ -16,6 +16,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/task_runner_util.h"
 #include "base/thread_task_runner_handle.h"
+#include "base/trace_event/trace_event.h"
 #include "chrome/browser/sync_file_system/file_change.h"
 #include "chrome/browser/sync_file_system/local/local_file_change_tracker.h"
 #include "chrome/browser/sync_file_system/local/local_file_sync_context.h"
@@ -715,6 +716,9 @@ void CannedSyncableFileSystem::DoGetUsageAndQuota(
     int64* usage,
     int64* quota,
     const storage::StatusCallback& callback) {
+  // crbug.com/349708
+  TRACE_EVENT0("io", "CannedSyncableFileSystem::DoGetUsageAndQuota");
+
   EXPECT_TRUE(io_task_runner_->RunsTasksOnCurrentThread());
   EXPECT_TRUE(is_filesystem_opened_);
   DCHECK(quota_manager_.get());