[Blob] Fix for resetting reader.

storage/browser/blob/upload_blob_element_reader.cc

 // Copyright 2015 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 "storage/browser/blob/upload_blob_element_reader.h"
 
 #include "net/base/net_errors.h"
 #include "storage/browser/blob/blob_data_handle.h"
 #include "storage/browser/blob/blob_reader.h"
 
 namespace storage {
 
 UploadBlobElementReader::UploadBlobElementReader(
     scoped_ptr<storage::BlobReader> reader,
     scoped_ptr<BlobDataHandle> handle)
     : reader_(reader.Pass()), handle_(handle.Pass()) {}
 
 UploadBlobElementReader::~UploadBlobElementReader() {}
 
 int UploadBlobElementReader::Init(const net::CompletionCallback& callback) {
+  if (reader_->reader_used()) {
+    reader_->Reset();
+  }
   BlobReader::Status status = reader_->CalculateSize(callback);
   switch (status) {
     case BlobReader::Status::NET_ERROR:
       return reader_->net_error();
     case BlobReader::Status::IO_PENDING:
       return net::ERR_IO_PENDING;
     case BlobReader::Status::DONE:
       return net::OK;
   }
   NOTREACHED();
@@ skipping 27 matching lines @@
   }
   NOTREACHED();
   return net::ERR_FAILED;
 }
 
 const std::string& UploadBlobElementReader::uuid() const {
   return handle_->uuid();
 }
 
 }  // namespace storage