Modify push_promise related methods to prepare for H3 push promise.

WritePushPromise() now returns void as no caller uses the returned size.
OnPushPromiseFrameStart() now takes in the frame lengths so that the frame can be consumed properly.

gfe-relnote: no prod behavior change, not protected.
PiperOrigin-RevId: 259377914
Change-Id: Ic89cdd785acf216e7fa5715426bbac30bf9b6045
diff --git a/quic/core/http/quic_spdy_session.h b/quic/core/http/quic_spdy_session.h
index d381d8c..8dfc47a 100644
--- a/quic/core/http/quic_spdy_session.h
+++ b/quic/core/http/quic_spdy_session.h
@@ -127,10 +127,9 @@
 
   // Write |headers| for |promised_stream_id| on |original_stream_id| in a
   // PUSH_PROMISE frame to peer.
-  // Return the size, in bytes, of the resulting PUSH_PROMISE frame.
-  virtual size_t WritePushPromise(QuicStreamId original_stream_id,
-                                  QuicStreamId promised_stream_id,
-                                  spdy::SpdyHeaderBlock headers);
+  virtual void WritePushPromise(QuicStreamId original_stream_id,
+                                QuicStreamId promised_stream_id,
+                                spdy::SpdyHeaderBlock headers);
 
   // Sends SETTINGS_MAX_HEADER_LIST_SIZE SETTINGS frame.
   void SendMaxHeaderListSize(size_t value);