Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/hpack/hpack_decoder3.cc

Index: net/spdy/hpack/hpack_decoder3.cc
diff --git a/net/spdy/hpack/hpack_decoder3.cc b/net/spdy/hpack/hpack_decoder3.cc
index 5c6fbb8bc907ed6b4dfc4a45710169fe5c30f72c..6929980158b14991022facddc2326e3a7aafe648 100644
--- a/net/spdy/hpack/hpack_decoder3.cc
+++ b/net/spdy/hpack/hpack_decoder3.cc
@@ -7,6 +7,7 @@
 #include "base/logging.h"
 #include "net/http2/decoder/decode_buffer.h"
 #include "net/http2/decoder/decode_status.h"
+#include "net/spdy/platform/api/spdy_estimate_memory_usage.h"
 
 using base::StringPiece;
 
@@ -107,6 +108,10 @@ void HpackDecoder3::set_max_decode_buffer_size_bytes(
   hpack_decoder_.set_max_string_size_bytes(max_decode_buffer_size_bytes);
 }
 
+size_t HpackDecoder3::EstimateMemoryUsage() const {
+  return SpdyEstimateMemoryUsage(hpack_decoder_);
+}
+
 HpackDecoder3::ListenerAdapter::ListenerAdapter() : handler_(nullptr) {}
 HpackDecoder3::ListenerAdapter::~ListenerAdapter() {}