[SyncFS] Add TaskLogger and wire up it.

chrome/browser/sync_file_system/drive_backend/sync_task_manager_unittest.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 <deque>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 57 matching lines @@
   // DriveFileSyncManager::Client overrides.
   virtual void MaybeScheduleNextTask() OVERRIDE {
     ++maybe_schedule_next_task_count_;
   }
   virtual void NotifyLastOperationStatus(
       SyncStatusCode last_operation_status,
       bool last_operation_used_network) OVERRIDE {
     last_operation_status_ = last_operation_status;
   }
 
+  virtual void RecordTaskLog(scoped_ptr<TaskLogger::TaskLog>) OVERRIDE {}
+
   void ScheduleTask(SyncStatusCode status_to_return,
                     const SyncStatusCallback& callback) {
     task_manager_->ScheduleTask(
         FROM_HERE,
         base::Bind(&TaskManagerClient::DoTask, AsWeakPtr(),
                    status_to_return, false /* idle */),
         SyncTaskManager::PRIORITY_MED,
         callback);
   }
 
@@ skipping 563 matching lines @@
 
   EXPECT_EQ("task1: finished", log[i++]);
 
   EXPECT_EQ("task2: updating to /hoge/fuga/piyo", log[i++]);
   EXPECT_EQ("task2: updated to /hoge/fuga/piyo", log[i++]);
   EXPECT_EQ("task2: finished", log[i++]);
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system