IndexedDB: Fixed support for empty blobs.

storage/browser/blob/blob_storage_context.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 "storage/browser/blob/blob_storage_context.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/bind.h"
@@ skipping 291 matching lines @@
   // 3) The FileSystem File item is denoted by the FileSystem URL, the range
   //    and the expected modification time.
   // 4) The Blob item is denoted by the source blob and an offset and size.
   //    Internal items that are fully used by the new blob (not cut by the
   //    offset or size) are shared between the blobs.  Otherwise, the relevant
   //    portion of the item is copied.
 
   const DataElement& data_element = blob_item->data_element();
   uint64 length = data_element.length();
   uint64 offset = data_element.offset();
-  DCHECK_GT(length, 0u);

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

Does this need to be removed now?

   UMA_HISTOGRAM_COUNTS("Storage.Blob.StorageSizeBeforeAppend",
                        memory_usage_ / 1024);
   switch (data_element.type()) {
     case DataElement::TYPE_BYTES:
       UMA_HISTOGRAM_COUNTS("Storage.BlobItemSize.Bytes", length / 1024);
       DCHECK(!offset);
       if (memory_usage_ + length > kMaxMemoryUsage) {
         exceeded_memory = true;
         break;
       }
@@ skipping 144 matching lines @@
   if (found == blob_map_.end())
     return false;
   return found->second->IsBeingBuilt();
 }
 
 bool BlobStorageContext::IsUrlRegistered(const GURL& blob_url) {
   return public_blob_urls_.find(blob_url) != public_blob_urls_.end();
 }
 
 }  // namespace storage