Replace QuicheStringPiece with absl::string_view

Tested:
    TAP --sample ran all affected tests and none failed
    http://test/OCL:335945932:BASE:335945937:1602110731512:c7c81ae9
PiperOrigin-RevId: 336088354
Change-Id: I6d9d2f77f21475068efc61d3b2c3434f752fb3b2

quic/masque/masque_encapsulated_client_session.h

diff --git a/quic/masque/masque_encapsulated_client_session.h b/quic/masque/masque_encapsulated_client_session.h
index 75ccc1f..11e9601 100644
--- a/quic/masque/masque_encapsulated_client_session.h
+++ b/quic/masque/masque_encapsulated_client_session.h
@@ -42,7 +42,7 @@
       const MasqueEncapsulatedClientSession&) = delete;
 
   // From MasqueClientSession::EncapsulatedClientSession.
-  void ProcessPacket(quiche::QuicheStringPiece packet,
+  void ProcessPacket(absl::string_view packet,
                      QuicSocketAddress server_address) override;
 
   // From QuicSession.