drive: Trigger "fast fetch" if remote update came during full loading.

chrome/browser/chromeos/drive/directory_loader.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/drive/directory_loader.h"
 
 #include "base/callback.h"
 #include "base/callback_helpers.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 378 matching lines @@
 
   int64 remote_changestamp = about_resource->largest_change_id();
 
   // Start loading the directory.
   int64 directory_changestamp = std::max(
       entry->directory_specific_info().changestamp(), *local_changestamp);
 
   DirectoryFetchInfo directory_fetch_info(
       local_id, entry->resource_id(), remote_changestamp);
 
-  // If the directory's changestamp is new enough, just schedule to run the
-  // callback, as there is no need to fetch the directory.
-  if (directory_changestamp + kMinimumChangestampGap > remote_changestamp) {
+  // If the directory's changestamp is up-to-date or the global changestamp of
+  // the metadata DB is new enough (which means the normal changelist loading
+  // should finish very soon), just schedule to run the callback, as there is no
+  // need to fetch the directory.
+  if (directory_changestamp >= remote_changestamp ||
+      *local_changestamp + kMinimumChangestampGap > remote_changestamp) {
     OnDirectoryLoadComplete(local_id, FILE_ERROR_OK);
   } else {
     // Start fetching the directory content, and mark it with the changestamp
     // |remote_changestamp|.
     LoadDirectoryFromServer(directory_fetch_info);
   }
 }
 
 void DirectoryLoader::OnDirectoryLoadComplete(const std::string& local_id,
                                               FileError error) {
@@ skipping 149 matching lines @@
   // Also notify the observers.
   if (error == FILE_ERROR_OK && !directory_path->empty()) {
     FOR_EACH_OBSERVER(ChangeListLoaderObserver,
                       observers_,
                       OnDirectoryReloaded(*directory_path));
   }
 }
 
 }  // namespace internal
 }  // namespace drive