Add QuicStringPiece which is actually StringPiece.

net/quic/chromium/crypto/channel_id_chromium.h

Index: net/quic/chromium/crypto/channel_id_chromium.h
diff --git a/net/quic/chromium/crypto/channel_id_chromium.h b/net/quic/chromium/crypto/channel_id_chromium.h
index 2c9869c30b2bd25fe4695c49e8b0b5855bfd012c..31ef722c404c874352a2bb89a9809af78ccacf86 100644
--- a/net/quic/chromium/crypto/channel_id_chromium.h
+++ b/net/quic/chromium/crypto/channel_id_chromium.h
@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "net/base/net_export.h"
 #include "net/quic/core/crypto/channel_id.h"
+#include "net/quic/platform/api/quic_string_piece.h"
 
 namespace crypto {
 class ECPrivateKey;
@@ -28,7 +29,7 @@ class NET_EXPORT_PRIVATE ChannelIDKeyChromium : public ChannelIDKey {
   ~ChannelIDKeyChromium() override;
 
   // ChannelIDKey interface
-  bool Sign(base::StringPiece signed_data,
+  bool Sign(QuicStringPiece signed_data,
             std::string* out_signature) const override;
   std::string SerializeKey() const override;