Migrating base::Closure() to base::DoNothing().

BUG=764795
TESTED=build

Change-Id: I45723edb2defc663df4228f26fa82e543aab567c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2497741Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Tomasz Tylenda <ttylenda@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828761}

chrome/browser/chromeos/arc/fileapi/arc_content_file_system_async_file_util.cc

@@ -45,7 +45,7 @@ void ArcContentFileSystemAsyncFileUtil::CreateOrOpen(
   NOTIMPLEMENTED();
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
-      base::BindOnce(std::move(callback), base::File(), base::Closure()));
+      base::BindOnce(std::move(callback), base::File(), base::OnceClosure()));
 }
 
 void ArcContentFileSystemAsyncFileUtil::EnsureFileExists(

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_async_file_util.cc

@@ -297,7 +297,7 @@ void ArcDocumentsProviderAsyncFileUtil::CreateOrOpen(
   // TODO(nya): Implement this function if it is ever called.
   NOTIMPLEMENTED();
   std::move(callback).Run(base::File(base::File::FILE_ERROR_INVALID_OPERATION),
-                          base::Closure());
+                          base::OnceClosure());
 }
 
 void ArcDocumentsProviderAsyncFileUtil::EnsureFileExists(