Change "&SomeQuicStringPiece[1]" to "SomeQuicStringPiece.data()+1"

This is neede because for Chromium, the former does not compile,
because of some subtle difference in the Chromium and Google3
implementations of QuicStringPiece.

gfe-relnote: N/A, test code only.
PiperOrigin-RevId: 275034631
Change-Id: I03c3b53bc4434b509f21f573bce1de59509b4a2c

quic/tools/quic_memory_cache_backend.cc

diff --git a/quic/tools/quic_memory_cache_backend.cc b/quic/tools/quic_memory_cache_backend.cc
index 9fe9dc5..6452d22 100644
--- a/quic/tools/quic_memory_cache_backend.cc
+++ b/quic/tools/quic_memory_cache_backend.cc
@@ -139,7 +139,7 @@
     uint64_t ignored = 0;
     if (generate_bytes_response_) {
       if (QuicTextUtils::StringToUint64(
-              QuicStringPiece(&path[1], path.size() - 1), &ignored)) {
+              QuicStringPiece(path.data() + 1, path.size() - 1), &ignored)) {
         // The actual parsed length is ignored here and will be recomputed
         // by the caller.
         return generate_bytes_response_.get();