Allow peers to pick low flow control limits in T099

Google QUIC requires flow control limits to be above 16K but IETF QUIC allows any values. In order to interoperate we need to allow low values in T099.

gfe-relnote: protected by disabled flag quic_supports_tls_handshake
PiperOrigin-RevId: 246002368
Change-Id: I5660e591256a355985877c2fb3c41fee06eb5a06
diff --git a/quic/core/quic_versions.h b/quic/core/quic_versions.h
index 160adeb..8da7361 100644
--- a/quic/core/quic_versions.h
+++ b/quic/core/quic_versions.h
@@ -147,6 +147,10 @@
   }
 
   bool KnowsWhichDecrypterToUse() const;
+
+  // Indicates that this QUIC version does not have an enforced minimum value
+  // for flow control values negotiated during the handshake.
+  bool AllowsLowFlowControlLimits() const;
 };
 
 QUIC_EXPORT_PRIVATE ParsedQuicVersion UnsupportedQuicVersion();