[BlobReader] Correct IsInMemory = false when async constructing

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 <stdint.h>
 
 #include "base/macros.h"
@@ skipping 13 matching lines @@
   virtual ~UploadElementReader() {}
 
   // 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;
 
+  // This function must be called before calling any other method. It is not
+  // valid to call any method (other than the destructor) if Init() fails.
+  // This method can be called multiple times. Calling this method after an
+  // Init() success results in resetting the state (i.e. the stream is rewound).
+  //
   // Initializes the instance synchronously when possible, otherwise does
   // initialization aynschronously, returns ERR_IO_PENDING and runs callback.
   // Calling this method again after a Init() success results in resetting the
   // state.
   virtual int Init(const CompletionCallback& callback) = 0;
 
   // Returns the byte-length of the element. For files that do not exist, 0
   // is returned. This is done for consistency with Mozilla.
   virtual uint64_t GetContentLength() const = 0;
 
@@ skipping 11 matching lines @@
                    int buf_length,
                    const CompletionCallback& callback) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(UploadElementReader);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_UPLOAD_ELEMENT_READER_H_