Add QuicStringPiece which is actually StringPiece.

net/quic/test_tools/fake_proof_source.h

Index: net/quic/test_tools/fake_proof_source.h
diff --git a/net/quic/test_tools/fake_proof_source.h b/net/quic/test_tools/fake_proof_source.h
index b6713f37716aa0d4f22ee2942773efb0b8940007..dad7aee6dc8fcb2dccdcf5012b78724d77a8f9fb 100644
--- a/net/quic/test_tools/fake_proof_source.h
+++ b/net/quic/test_tools/fake_proof_source.h
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "net/quic/core/crypto/proof_source.h"
+#include "net/quic/platform/api/quic_string_piece.h"
 
 namespace net {
 namespace test {
@@ -34,7 +35,7 @@ class FakeProofSource : public ProofSource {
                 const std::string& hostname,
                 const std::string& server_config,
                 QuicVersion quic_version,
-                base::StringPiece chlo_hash,
+                QuicStringPiece chlo_hash,
                 const QuicTagVector& connection_options,
                 std::unique_ptr<ProofSource::Callback> callback) override;