Set root resource ID upon full feed update.

chrome/browser/chromeos/drive/drive_feed_loader.h

Index: chrome/browser/chromeos/drive/drive_feed_loader.h
diff --git a/chrome/browser/chromeos/drive/drive_feed_loader.h b/chrome/browser/chromeos/drive/drive_feed_loader.h
index 95d5fa07ecfe22e657c4faef6ca49254bf77481e..9f1c39fbc23a2b2bfa80020c00a5c5f21d77c284 100644
--- a/chrome/browser/chromeos/drive/drive_feed_loader.h
+++ b/chrome/browser/chromeos/drive/drive_feed_loader.h
@@ -76,6 +76,9 @@ struct LoadFeedParams {
   FileOperationCallback load_finished_callback;
   ScopedVector<google_apis::DocumentFeed> feed_list;
   scoped_ptr<GetDocumentsUiState> ui_state;
+  // On initial feed load for Drive API, remember root ID for
+  // DriveResourceData initialization later in UpdateFromFeed().
+  std::string root_resource_id;
 };
 
 // Defines set of parameters sent to callback OnProtoLoaded().
@@ -148,10 +151,12 @@ class DriveFeedLoader {
   //
   // See comments at DriveFeedProcessor::ApplyFeeds() for
   // |start_changestamp| and |root_feed_changestamp|.
+  // |root_resource_id| is used for Drive API.
   void UpdateFromFeed(
-    const ScopedVector<google_apis::DocumentFeed>& feed_list,
-    int64 start_changestamp,
-    int64 root_feed_changestamp);
+      const ScopedVector<google_apis::DocumentFeed>& feed_list,
+      int64 start_changestamp,
+      int64 root_feed_changestamp,
+      const std::string& root_resource_id);
 
   // Indicates whether there is a feed refreshing server request is in flight.
   bool refreshing() const { return refreshing_; }