Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/hpack/hpack_decoder3.h

 // Copyright 2017 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_SPDY_HPACK_HPACK_DECODER3_H_
 #define NET_SPDY_HPACK_HPACK_DECODER3_H_
 
 // HpackDecoder3 implements HpackDecoderInterface, using Http2HpackDecoder to
 // decode HPACK blocks into HTTP/2 header lists as outlined in
 // http://tools.ietf.org/html/rfc7541.
@@ skipping 32 matching lines @@
       SpdyHeadersHandlerInterface* handler) override;
   bool HandleControlFrameHeadersData(const char* headers_data,
                                      size_t headers_data_length) override;
   bool HandleControlFrameHeadersComplete(size_t* compressed_len) override;
   const SpdyHeaderBlock& decoded_block() const override;
   void SetHeaderTableDebugVisitor(
       std::unique_ptr<HpackHeaderTable::DebugVisitorInterface> visitor)
       override;
   void set_max_decode_buffer_size_bytes(
       size_t max_decode_buffer_size_bytes) override;
+  size_t EstimateMemoryUsage() const override;
 
  private:
   class NET_EXPORT_PRIVATE ListenerAdapter
       : public HpackDecoderListener,
         public HpackDecoderTablesDebugListener {
    public:
     ListenerAdapter();
     ~ListenerAdapter() override;
 
     // If a SpdyHeadersHandlerInterface is provided, the decoder will emit
@@ skipping 55 matching lines @@
   // moment because HandleControlFrameHeadersStart won't be called if a handler
   // is not being provided by the caller.
   bool header_block_started_;
 
   DISALLOW_COPY_AND_ASSIGN(HpackDecoder3);
 };
 
 }  // namespace net
 
 #endif  // NET_SPDY_HPACK_HPACK_DECODER3_H_