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..121324ae2cfebd6c9943420983be8f4bc5554b1e 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 "base/trace_event/memory_usage_estimator.h"
 
 namespace net {
 
@@ -92,4 +93,8 @@ void HpackOutputStream::BoundedTakeString(size_t max_size, string* output) {
   }
 }
 
+size_t HpackOutputStream::EstimateMemoryUsage() const {
+  return base::trace_event::EstimateMemoryUsage(buffer_);
+}
+
 }  // namespace net