Adds code in ShinkansenClient to count metadata bytes as part of the total response size.

gfe-relnote: n/a (test utilities only)
PiperOrigin-RevId: 253845535
Change-Id: I1f3d6635f841f57b74eeebb450818c92245c2084

spdy/core/http2_frame_decoder_adapter.h

diff --git a/spdy/core/http2_frame_decoder_adapter.h b/spdy/core/http2_frame_decoder_adapter.h
index 02deafd..86489c6 100644
--- a/spdy/core/http2_frame_decoder_adapter.h
+++ b/spdy/core/http2_frame_decoder_adapter.h
@@ -94,6 +94,9 @@
   // Set extension callbacks to be called from the framer or decoder. Optional.
   // If called multiple times, only the last visitor will be used.
   void set_extension_visitor(spdy::ExtensionVisitorInterface* visitor);
+  spdy::ExtensionVisitorInterface* extension_visitor() const {
+    return extension_;
+  }
 
   // Set debug callbacks to be called from the framer. The debug visitor is
   // completely optional and need not be set in order for normal operation.