[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 storage {
+class UploadBlobElementReader;
+}
+
 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;
+  virtual const storage::UploadBlobElementReader*
+  AsUploadBlobElementReaderForTests() const;

[mmenke, 2015/09/14 19:24:33]

This method is a layering violation.  Net shouldn't know what an upload blob
element reader is.  I'd suggest just casting instead, much as I dislike explicit
casting.

[dmurph, 2015/09/14 20:27:50]

Sounds good.  Done.

 
   // 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
@@ skipping 20 matching lines @@
                    int buf_length,
                    const CompletionCallback& callback) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(UploadElementReader);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_UPLOAD_ELEMENT_READER_H_