Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/hpack/hpack_output_stream.cc

Index: net/spdy/hpack/hpack_output_stream.cc
diff --git a/net/spdy/hpack/hpack_output_stream.cc b/net/spdy/hpack/hpack_output_stream.cc
index 6337d7d42e85eb244fc9b762fed346c85106c2ce..a93965d1f10dc06e636ee7709ec14dc4b4b515e1 100644
--- a/net/spdy/hpack/hpack_output_stream.cc
+++ b/net/spdy/hpack/hpack_output_stream.cc
@@ -7,6 +7,7 @@
 #include <utility>
 
 #include "base/logging.h"
+#include "net/spdy/platform/api/spdy_estimate_memory_usage.h"
 
 namespace net {
 
@@ -92,4 +93,8 @@ void HpackOutputStream::BoundedTakeString(size_t max_size, string* output) {
   }
 }
 
+size_t HpackOutputStream::EstimateMemoryUsage() const {
+  return SpdyEstimateMemoryUsage(buffer_);
+}
+
 }  // namespace net