Initialize root resource ID only once for Drive API.

chrome/browser/chromeos/drive/drive_feed_loader.cc

Index: chrome/browser/chromeos/drive/drive_feed_loader.cc
diff --git a/chrome/browser/chromeos/drive/drive_feed_loader.cc b/chrome/browser/chromeos/drive/drive_feed_loader.cc
index 605ceb1430a27a9284dc5c39c26122041a9b90fd..09a1f293e2d29f30eccdb5a5160668ceed79e91e 100644
--- a/chrome/browser/chromeos/drive/drive_feed_loader.cc
+++ b/chrome/browser/chromeos/drive/drive_feed_loader.cc
@@ -381,7 +381,10 @@ void DriveFeedLoader::OnGetAboutResource(
 
   bool changes_detected = true;
   int64 largest_changestamp = about_resource->largest_change_id();
-  resource_metadata_->InitializeRootEntry(about_resource->root_folder_id());
+
+  // Initialize the root entry only for the first time.
+  if (resource_metadata_->root_resource_id().empty())
+    resource_metadata_->InitializeRootEntry(about_resource->root_folder_id());
 
   if (local_changestamp >= largest_changestamp) {
     if (local_changestamp > largest_changestamp) {