Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/spdy/hpack/hpack_output_stream.h

Index: net/spdy/hpack/hpack_output_stream.h
diff --git a/net/spdy/hpack/hpack_output_stream.h b/net/spdy/hpack/hpack_output_stream.h
index 41dfd7d4f4f056fb3b516c42f51308213e365d97..965cea797a3ccd315258145a1eff650ec3fc6ee1 100644
--- a/net/spdy/hpack/hpack_output_stream.h
+++ b/net/spdy/hpack/hpack_output_stream.h
@@ -59,6 +59,9 @@ class NET_EXPORT_PRIVATE HpackOutputStream {
   // Size in bytes of stream's internal buffer.
   size_t size() const { return buffer_.size(); }
 
+  // Returns the estimate of dynamically allocated memory in bytes.
+  size_t EstimateMemoryUsage() const;
+
  private:
   // The internal bit buffer.
   std::string buffer_;