Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/hpack/hpack_encoder.cc

Index: net/spdy/hpack/hpack_encoder.cc
diff --git a/net/spdy/hpack/hpack_encoder.cc b/net/spdy/hpack/hpack_encoder.cc
index 0ec5e8f67d4a3cdabc71b07f0c86dbeca509a343..04bdaea10a0c811f3aa4685d14a6d71335c581cc 100644
--- a/net/spdy/hpack/hpack_encoder.cc
+++ b/net/spdy/hpack/hpack_encoder.cc
@@ -9,6 +9,7 @@
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/trace_event/memory_usage_estimator.h"
 #include "net/spdy/hpack/hpack_constants.h"
 #include "net/spdy/hpack/hpack_header_table.h"
 #include "net/spdy/hpack/hpack_huffman_table.h"
@@ -132,6 +133,12 @@ void HpackEncoder::ApplyHeaderTableSizeSetting(size_t size_setting) {
   should_emit_table_size_ = true;
 }
 
+size_t HpackEncoder::EstimateMemoryUsage() const {
+  // |huffman_table_| is a singleton. It's accounted for in spdy_session_pool.cc
+  return base::trace_event::EstimateMemoryUsage(header_table_) +
+         base::trace_event::EstimateMemoryUsage(output_stream_);
+}
+
 void HpackEncoder::EncodeRepresentations(RepresentationIterator* iter,
                                          string* output) {
   MaybeEmitTableSize();