[SyncFS] Force activate folder tracker on folder creation conflict case

chrome/browser/sync_file_system/drive_backend/metadata_database.cc

 // Copyright 2013 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/sync_file_system/drive_backend/metadata_database.h"
 
 #include <algorithm>
 #include <stack>
 
 #include "base/bind.h"
@@ skipping 981 matching lines @@
   //   - There is no active tracker that has the same |parent| and |title|.
   if (!tracker->active() && CanActivateTracker(*tracker))
     MakeTrackerActive(tracker->tracker_id(), batch.get());
   if (tracker->dirty() && !ShouldKeepDirty(*tracker))
     ClearDirty(tracker, NULL);
   PutFileTrackerToBatch(*tracker, batch.get());
 
   WriteToDatabase(batch.Pass(), callback);
 }
 
-MetadataDatabase::ActivationStatus MetadataDatabase::TryNoSideEffectActivation(
+MetadataDatabase::ActivationStatus MetadataDatabase::TryActivateTracker(
     int64 parent_tracker_id,
     const std::string& file_id,
     const SyncStatusCallback& callback) {
   DCHECK(ContainsKey(tracker_by_id_, parent_tracker_id));
   DCHECK(ContainsKey(file_by_id_, file_id));
 
   FileMetadata file;
   if (!FindFileByFileID(file_id, &file)) {
     NOTREACHED();
     RunSoon(FROM_HERE, base::Bind(callback, SYNC_STATUS_FAILED));
     return ACTIVATION_PENDING;
   }
   std::string title = file.details().title();
   DCHECK(!HasInvalidTitle(title));
 
   TrackerSet same_file_id;
   FindTrackersByFileID(file_id, &same_file_id);
 
+  // Pick up the tracker to be activated, that has:
+  //  - |parent_tarcker_id| as the parent, and
+  //  - |file_id| as the tracker's |file_id|.
   FileTracker* tracker = NULL;
   for (TrackerSet::iterator itr = same_file_id.begin();
        itr != same_file_id.end(); ++itr) {
     FileTracker* candidate = *itr;
     if (candidate->parent_tracker_id() != parent_tracker_id)
       continue;
 
     if (candidate->has_synced_details() &&
         candidate->synced_details().title() != title)
       continue;
     tracker = candidate;
   }
 
   DCHECK(tracker);
 
+  // Check if there is another active tracker that tracks |file_id|.
+  // This can happen when the tracked file has multiple parents.
+  // If this case, report the failure to the caller.
+  if (!tracker->active() && same_file_id.has_active())
+    return ACTIVATION_FAILED_ANOTHER_ACTIVE_TRACKER;
+
+  scoped_ptr<leveldb::WriteBatch> batch(new leveldb::WriteBatch);
+
   if (!tracker->active()) {
-    if (same_file_id.has_active())
-      return ACTIVATION_FAILED_ANOTHER_ACTIVE_TRACKER;
-
+    // Check if there is another active tracker that has the same path to
+    // the tracker to be activated.
+    // Assuming the caller already overrides local file with newly added file,
+    // inactivate existing active tracker.
     TrackerSet same_title;
     FindTrackersByParentAndTitle(parent_tracker_id, title, &same_title);
-    if (same_title.has_active())
-      return ACTIVATION_FAILED_SAME_PATH_TRACKER;
+    if (same_title.has_active()) {
+      MakeTrackerInactive(same_title.active_tracker()->tracker_id(),
+                          batch.get());
+    }
   }
 
-  scoped_ptr<leveldb::WriteBatch> batch(new leveldb::WriteBatch);
   if (!tracker->has_synced_details() ||
       tracker->synced_details().title() != title) {
     trackers_by_parent_and_title_[parent_tracker_id]
         [GetTrackerTitle(*tracker)].Erase(tracker);
     trackers_by_parent_and_title_[parent_tracker_id][title].Insert(
         tracker);
   }
   *tracker->mutable_synced_details() = file.details();
 
   MakeTrackerActive(tracker->tracker_id(), batch.get());
@@ skipping 990 matching lines @@
     MakeTrackerActive(tracker->tracker_id(), batch);
     ClearDirty(tracker, batch);
     return;
   }
 
   NOTREACHED();
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system