Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/hpack/hpack_header_table.h

Index: net/spdy/hpack/hpack_header_table.h
diff --git a/net/spdy/hpack/hpack_header_table.h b/net/spdy/hpack/hpack_header_table.h
index ca0318a810778e123dba6be56a1e5401047c63da..a3b5744f3b8bca8428c126badf58da265ea3f085 100644
--- a/net/spdy/hpack/hpack_header_table.h
+++ b/net/spdy/hpack/hpack_header_table.h
@@ -125,6 +125,9 @@ class NET_EXPORT_PRIVATE HpackHeaderTable {
     debug_visitor_ = std::move(visitor);
   }
 
+  // Returns the estimate of dynamically allocated memory in bytes.
+  size_t EstimateMemoryUsage() const;
+
  private:
   // Returns number of evictions required to enter |name| & |value|.
   size_t EvictionCountForEntry(base::StringPiece name,