Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/hpack/hpack_decoder_interface.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_SPDY_HPACK_HPACK_DECODER_INTERFACE_H_
 #define NET_SPDY_HPACK_HPACK_DECODER_INTERFACE_H_
 
 // HpackDecoderInterface is the base class for HPACK block decoders.
 // HPACK is defined in http://tools.ietf.org/html/rfc7541
 
@@ skipping 48 matching lines @@
       std::unique_ptr<HpackHeaderTable::DebugVisitorInterface> visitor) = 0;
 
   // Set how much encoded data this decoder is willing to buffer.
   // TODO(jamessynge): Resolve definition of this value, as it is currently
   // too tied to a single implementation. We probably want to limit one or more
   // of these: individual name or value strings, header entries, the entire
   // header list, or the HPACK block; we probably shouldn't care about the size
   // of individual transport buffers.
   virtual void set_max_decode_buffer_size_bytes(
       size_t max_decode_buffer_size_bytes) = 0;
+
+  // Returns the estimate of dynamically allocated memory in bytes.
+  virtual size_t EstimateMemoryUsage() const = 0;
 };
 
 }  // namespace net
 
 #endif  // NET_SPDY_HPACK_HPACK_DECODER_INTERFACE_H_