[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"
+#include "storage/browser/fileapi/file_system_context.h"
 
 namespace storage {
 
 UploadBlobElementReader::UploadBlobElementReader(
-    scoped_ptr<storage::BlobReader> reader,
-    scoped_ptr<BlobDataHandle> handle)
-    : reader_(reader.Pass()), handle_(handle.Pass()) {}
+    scoped_ptr<BlobDataHandle> handle,
+    FileSystemContext* file_system_context,
+    base::SingleThreadTaskRunner* file_task_runner)
+    : handle_(handle.Pass()),
+      file_system_context_(file_system_context),
+      file_runner_(file_task_runner) {
+  reader_ = handle_->CreateReader(file_system_context, file_task_runner);
+}
 
 UploadBlobElementReader::~UploadBlobElementReader() {}
 
 int UploadBlobElementReader::Init(const net::CompletionCallback& callback) {
+  if (reader_->dirty()) {
+    reader_ =
+        handle_->CreateReader(file_system_context_.get(), file_runner_.get());

[michaeln, 2015/12/11 02:17:01]

i think this is a nice improvement!

i think you could always create a new reader_ here and never in the ctor

+  }
   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