Use constexpr TaskTraits constructor in extensions.

extensions/browser/api/file_handlers/directory_util.cc

 // Copyright 2016 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 "extensions/browser/api/file_handlers/directory_util.h"
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/task_scheduler/post_task.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 25 matching lines @@
 #if defined(OS_CHROMEOS)
   NonNativeFileSystemDelegate* delegate =
       ExtensionsAPIClient::Get()->GetNonNativeFileSystemDelegate();
   if (delegate && delegate->IsUnderNonNativeLocalPath(context, path)) {
     delegate->IsNonNativeLocalPathDirectory(context, path, callback);
     return;
   }
 #endif
 
   base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE, base::TaskTraits().MayBlock(),
+      FROM_HERE, {base::MayBlock()},
       base::Bind(&GetIsDirectoryFromFileInfo, path), callback);
 }
 
 }  // namespace
 
 IsDirectoryCollector::IsDirectoryCollector(content::BrowserContext* context)
     : context_(context), left_(0), weak_ptr_factory_(this) {}
 
 IsDirectoryCollector::~IsDirectoryCollector() {}
 
@@ skipping 32 matching lines @@
         FROM_HERE, base::Bind(callback_, base::Passed(&result_)));
     // Release the callback to avoid a circullar reference in case an instance
     // of this class is a member of a ref counted class, which instance is bound
     // to this callback.
     callback_ = CompletionCallback();
   }
 }
 
 }  // namespace app_file_handler_util
 }  // namespace extensions