Revert of [Blob] BlobReader class & tests, and removal of all redundant reading.

net/base/upload_element_reader.h

 // Copyright (c) 2012 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.
 
 #ifndef NET_BASE_UPLOAD_ELEMENT_READER_H_
 #define NET_BASE_UPLOAD_ELEMENT_READER_H_
 
 #include "base/basictypes.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_export.h"
 
 namespace net {
 
 class IOBuffer;
 class UploadBytesElementReader;
+class UploadDiskCacheEntryElementReader;
 class UploadFileElementReader;
 
 // An interface to read an upload data element.
 class NET_EXPORT UploadElementReader {
  public:
   UploadElementReader() {}
   virtual ~UploadElementReader() {}
 
+  // Returns this instance's pointer as UploadDiskCacheEntryElementReader when
+  // possible, otherwise returns nullptr.
+  virtual const UploadDiskCacheEntryElementReader*
+  AsDiskCacheEntryReaderForTests() const;
+
   // Returns this instance's pointer as UploadBytesElementReader when possible,
   // otherwise returns NULL.
   virtual const UploadBytesElementReader* AsBytesReader() const;
 
   // Returns this instance's pointer as UploadFileElementReader when possible,
   // otherwise returns NULL.
   virtual const UploadFileElementReader* AsFileReader() const;
 
   // Initializes the instance synchronously when possible, otherwise does
   // initialization aynschronously, returns ERR_IO_PENDING and runs callback.
@@ skipping 19 matching lines @@
                    int buf_length,
                    const CompletionCallback& callback) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(UploadElementReader);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_UPLOAD_ELEMENT_READER_H_