[BlobStorage] Better net error reporting for pre-broken blobs

storage/browser/blob/blob_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/blob_reader.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 57 matching lines @@
 BlobReader::FileStreamReaderProvider::~FileStreamReaderProvider() {}
 
 BlobReader::BlobReader(
     const BlobDataHandle* blob_handle,
     std::unique_ptr<FileStreamReaderProvider> file_stream_provider,
     base::SequencedTaskRunner* file_task_runner)
     : file_stream_provider_(std::move(file_stream_provider)),
       file_task_runner_(file_task_runner),
       net_error_(net::OK),
       weak_factory_(this) {
-  if (blob_handle && !blob_handle->IsBroken()) {
-    blob_handle_.reset(new BlobDataHandle(*blob_handle));
+  if (blob_handle) {
+    if (!blob_handle->IsBroken()) {

[pwnall, 2017/02/22 23:33:50]

How about flipping the if / else, so no (implicit) double negative shows up when
thinking about condition gating the else branch?

[dmurph, 2017/02/22 23:43:25]

Good idea, thanks.

+      blob_handle_.reset(new BlobDataHandle(*blob_handle));
+    } else {
+      net_error_ = ConvertBlobErrorToNetError(blob_handle->GetBlobStatus());
+    }
   }
 }
 
 BlobReader::~BlobReader() {
 }
 
 BlobReader::Status BlobReader::CalculateSize(
     const net::CompletionCallback& done) {
   DCHECK(!total_size_calculated_);
   DCHECK(size_callback_.is_null());
@@ skipping 575 matching lines @@
 void BlobReader::SetFileReaderAtIndex(
     size_t index,
     std::unique_ptr<FileStreamReader> reader) {
   if (reader)
     index_to_reader_[index] = std::move(reader);
   else
     index_to_reader_.erase(index);
 }
 
 }  // namespace storage