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 2342 matching lines @@
                      bytes_written_));
     }
   }
 
   void WriteBlobToFileOnIOThread(const FilePath& file_path,
                                  const GURL& blob_url,
                                  const base::Time& last_modified,
                                  net::URLRequestContext* request_context) {
     DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
     scoped_ptr<storage::FileStreamWriter> writer(
-        storage::FileStreamWriter::CreateForLocalFile(
-            task_runner_.get(),
-            file_path,
-            0,
-            storage::FileStreamWriter::CREATE_NEW_FILE));
+        storage::FileStreamWriter::CreateForLocalFile(task_runner_.get(),
+                                                      file_path, 0));
     scoped_ptr<FileWriterDelegate> delegate(new FileWriterDelegate(
         writer.Pass(), storage::FlushPolicy::FLUSH_ON_COMPLETION));
 
     DCHECK(blob_url.is_valid());
     scoped_ptr<net::URLRequest> blob_request(request_context->CreateRequest(
         blob_url, net::DEFAULT_PRIORITY, delegate.get(), NULL));
 
     this->file_path_ = file_path;
     this->last_modified_ = last_modified;
 
@@ skipping 71 matching lines @@
     task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&Transaction::ChainedBlobWriter::ReportWriteCompletion,
                    chained_blob_writer,
                    true,
                    info.size));
   } else {
     DCHECK(descriptor.url().is_valid());
     scoped_refptr<LocalWriteClosure> write_closure(
         new LocalWriteClosure(chained_blob_writer, task_runner_.get()));
+    {
+      // FileStreamWriter needs an existing file, so create one now.
+      base::File file(path,

[jsbell, 2015/03/03 01:01:48]

Should we do this in WriteBlobToFileOnIOThread instead, to avoid stalling the
IDB thread on this I/O?

[cmumford, 2015/03/03 22:26:09]

Can't do file I/O on that thread - only reason why it's here.

+                      base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE);

[michaeln, 2015/03/03 00:02:51]

nit: ditto file.Close()

[cmumford, 2015/03/03 22:26:09]

Done.

+    }
     content::BrowserThread::PostTask(
         content::BrowserThread::IO,
         FROM_HERE,
         base::Bind(&LocalWriteClosure::WriteBlobToFileOnIOThread,
                    write_closure.get(),
                    path,
                    descriptor.url(),
                    descriptor.last_modified(),
                    request_context_));
   }
@@ skipping 1935 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