[SyncFS] Add exclusive task support for TaskDependencyManager

chrome/browser/sync_file_system/drive_backend/task_dependency_manager.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/sync_file_system/drive_backend/task_dependency_manager.h"
 
 #include <utility>
 
 #include "base/logging.h"
 
@@ skipping 41 matching lines @@
       for (itr = paths_to_insert.begin(); itr != end; ++itr)
         paths->erase(*itr);
       return false;
     }
   }
   return true;
 }
 
 }  // namespace
 
-BlockingFactor::BlockingFactor() {}
+BlockingFactor::BlockingFactor() : exclusive(false) {}
 BlockingFactor::~BlockingFactor() {}
 
-TaskDependencyManager::TaskDependencyManager() {}
+TaskDependencyManager::TaskDependencyManager()
+    : running_exclusive_task_(false) {}
 
 TaskDependencyManager::~TaskDependencyManager() {
   DCHECK(paths_by_app_id_.empty());
   DCHECK(file_ids_.empty());
   DCHECK(tracker_ids_.empty());
 }
 
 bool TaskDependencyManager::Insert(const BlockingFactor& blocking_factor) {
+  if (running_exclusive_task_)
+    return false;
+
+  if (blocking_factor.exclusive) {
+    if (!tracker_ids_.empty() ||
+        !file_ids_.empty() ||
+        !paths_by_app_id_.empty())
+      return false;
+    running_exclusive_task_ = true;
+    return true;
+  }
+
   if (!InsertAllOrNone(blocking_factor.tracker_ids, &tracker_ids_))
     goto fail_on_tracker_id_insertion;
 
   if (!InsertAllOrNone(blocking_factor.file_ids, &file_ids_))
     goto fail_on_file_id_insertion;
 
   if (!blocking_factor.app_id.empty() &&
       !InsertPaths(blocking_factor.paths,
                    &paths_by_app_id_[blocking_factor.app_id])) {
     if (paths_by_app_id_[blocking_factor.app_id].empty())
       paths_by_app_id_.erase(blocking_factor.app_id);
     goto fail_on_path_insertion;
   }
 
   return true;
 
  fail_on_path_insertion:
   EraseContainer(blocking_factor.file_ids, &file_ids_);
  fail_on_file_id_insertion:
   EraseContainer(blocking_factor.tracker_ids, &tracker_ids_);
  fail_on_tracker_id_insertion:
 
   return false;
 }
 
 void TaskDependencyManager::Erase(const BlockingFactor& blocking_factor) {
+  if (blocking_factor.exclusive) {
+    DCHECK(running_exclusive_task_);
+    DCHECK(paths_by_app_id_.empty());
+    DCHECK(file_ids_.empty());
+    DCHECK(tracker_ids_.empty());
+
+    running_exclusive_task_ = false;
+    return;
+  }
+
   if (!blocking_factor.app_id.empty()) {
     EraseContainer(blocking_factor.paths,
                    &paths_by_app_id_[blocking_factor.app_id]);
     if (paths_by_app_id_[blocking_factor.app_id].empty())
       paths_by_app_id_.erase(blocking_factor.app_id);
   }
 
   EraseContainer(blocking_factor.file_ids, &file_ids_);
   EraseContainer(blocking_factor.tracker_ids, &tracker_ids_);
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system