Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/http2/hpack/decoder/hpack_decoder_string_buffer.h

 // Copyright 2016 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_HTTP2_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_
 #define NET_HTTP2_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_
 
 // HpackDecoderStringBuffer helps an HPACK decoder to avoid copies of a string
 // literal (name or value) except when necessary (e.g. when split across two
 // or more HPACK block fragments).
@@ skipping 44 matching lines @@
   // effort to avoid unnecessary copies. ReleaseString() must not be called
   // unless the string has been buffered (to avoid forcing a potentially
   // unnecessary copy). ReleaseString() also resets the instance so that it can
   // be used to collect another string.
   std::string ReleaseString();
 
   State state_for_testing() const { return state_; }
   Backing backing_for_testing() const { return backing_; }
   void OutputDebugStringTo(std::ostream& out) const;
 
+  // Returns the estimate of dynamically allocated memory in bytes.
+  size_t EstimateMemoryUsage() const;
+
  private:
   // Storage for the string being buffered, if buffering is necessary
   // (e.g. if Huffman encoded, buffer_ is storage for the decoded string).
   std::string buffer_;
 
   // The StringPiece to be returned by HpackDecoderStringBuffer::str(). If a
   // string has been collected, but not buffered, value_ points to that string.
   base::StringPiece value_;
 
   // The decoder to use if the string is Huffman encoded.
@@ skipping 13 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(HpackDecoderStringBuffer);
 };
 
 NET_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& out,
                                             const HpackDecoderStringBuffer& v);
 
 }  // namespace net
 
 #endif  // NET_HTTP2_HPACK_DECODER_HPACK_DECODER_STRING_BUFFER_H_