IndexedDB: Fixed support for empty blobs.

content/browser/indexed_db/indexed_db_backing_store.cc

Index: content/browser/indexed_db/indexed_db_backing_store.cc
diff --git a/content/browser/indexed_db/indexed_db_backing_store.cc b/content/browser/indexed_db/indexed_db_backing_store.cc
index 4ae9ed4f236722b4c76dbcb62ee677b4223794c9..fdc072826a6490d40e81ad00ac08a08cd5a2a454 100644
--- a/content/browser/indexed_db/indexed_db_backing_store.cc
+++ b/content/browser/indexed_db/indexed_db_backing_store.cc
@@ -2339,8 +2339,12 @@ class LocalWriteClosure : public FileWriterDelegate::DelegateWriteCallback,
     }
 
     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.
+      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 {
@@ -2403,6 +2407,19 @@ class LocalWriteClosure : public FileWriterDelegate::DelegateWriteCallback,
     chained_blob_writer_->ReportWriteCompletion(true, bytes_written_);
   }
 
+  // Create an empty file.
+  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_;