net: Introduce SeekableIOBuffer and clean up HttpStreamParser.

net/http/http_stream_parser.h

Index: net/http/http_stream_parser.h
diff --git a/net/http/http_stream_parser.h b/net/http/http_stream_parser.h
index 861fbe9402956e1e22b6f0468b0947a6f70b4ea0..97e378e20b9c93211152e11ec476fe5ca91b0a0d 100644
--- a/net/http/http_stream_parser.h
+++ b/net/http/http_stream_parser.h
@@ -26,6 +26,7 @@ class HttpRequestHeaders;
 class HttpResponseInfo;
 class IOBuffer;
 class IOBufferWithSize;
+class SeekableIOBuffer;
 class SSLCertRequestInfo;
 class SSLInfo;
 
@@ -223,9 +224,7 @@ class NET_EXPORT_PRIVATE HttpStreamParser  : public ChunkCallback {
 
   // Stores an encoded chunk for chunked uploads.
   // Note: This should perhaps be improved to not create copies of the data.
-  scoped_refptr<IOBufferWithSize> raw_chunk_buf_;
-  // Wraps raw_chunk_buf_ to read the remaining data progressively.
-  scoped_refptr<DrainableIOBuffer> chunk_buf_;
+  scoped_refptr<SeekableIOBuffer> chunk_buf_;
   size_t chunk_length_without_encoding_;
   bool sent_last_chunk_;