IndexedDB: Fixed support for empty blobs.

content/browser/indexed_db/indexed_db_backing_store.cc

 // Copyright (c) 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 "content/browser/indexed_db/indexed_db_backing_store.h"
 
 #include <algorithm>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
@@ skipping 2321 matching lines @@
     if (write_status == FileWriterDelegate::SUCCESS_IO_PENDING)
       return;  // We don't care about progress events.
     if (rv == base::File::FILE_OK) {
       DCHECK_EQ(write_status, FileWriterDelegate::SUCCESS_COMPLETED);
     } else {
       DCHECK(write_status == FileWriterDelegate::ERROR_WRITE_STARTED ||
              write_status == FileWriterDelegate::ERROR_WRITE_NOT_STARTED);
     }
 
     bool success = write_status == FileWriterDelegate::SUCCESS_COMPLETED;
-
-    if (success && !last_modified_.is_null()) {
+    if (success && !bytes_written_) {
+      // LocalFileStreamWriter only creates a file if data is actually written.
+      // If none was then create one now.

[michaeln, 2015/03/06 22:31:38]

nit: the first line of this comment is enough

+      task_runner_->PostTask(
+          FROM_HERE, base::Bind(&LocalWriteClosure::CreateEmptyFile, this));
+    } else if (success && !last_modified_.is_null()) {
       task_runner_->PostTask(
           FROM_HERE, base::Bind(&LocalWriteClosure::UpdateTimeStamp, this));
     } else {
       task_runner_->PostTask(
           FROM_HERE,
           base::Bind(&IndexedDBBackingStore::Transaction::ChainedBlobWriter::
                      ReportWriteCompletion,
                      chained_blob_writer_,
                      success,
                      bytes_written_));
@@ skipping 42 matching lines @@
   // If necessary, update the timestamps on the file as a final
   // step before reporting success.
   void UpdateTimeStamp() {
     DCHECK(task_runner_->RunsTasksOnCurrentThread());
     if (!base::TouchFile(file_path_, last_modified_, last_modified_)) {
       // TODO(ericu): Complain quietly; timestamp's probably not vital.
     }
     chained_blob_writer_->ReportWriteCompletion(true, bytes_written_);
   }
 
+  // Create an empty file.

[michaeln, 2015/03/06 22:31:38]

this comment probably isn't needed

+  void CreateEmptyFile() {
+    DCHECK(task_runner_->RunsTasksOnCurrentThread());
+    base::File file(file_path_,
+                    base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE);
+    bool success = file.created();
+    file.Close();
+    if (success && !last_modified_.is_null())
+      UpdateTimeStamp();
+    else
+      chained_blob_writer_->ReportWriteCompletion(success, bytes_written_);
+  }
+
   scoped_refptr<IndexedDBBackingStore::Transaction::ChainedBlobWriter>
       chained_blob_writer_;
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
   int64 bytes_written_;
 
   base::FilePath file_path_;
   base::Time last_modified_;
 
   DISALLOW_COPY_AND_ASSIGN(LocalWriteClosure);
 };
@@ skipping 1988 matching lines @@
 
 IndexedDBBackingStore::Transaction::WriteDescriptor::WriteDescriptor(
     const WriteDescriptor& other) = default;
 IndexedDBBackingStore::Transaction::WriteDescriptor::~WriteDescriptor() =
     default;
 IndexedDBBackingStore::Transaction::WriteDescriptor&
     IndexedDBBackingStore::Transaction::WriteDescriptor::
     operator=(const WriteDescriptor& other) = default;
 
 }  // namespace content