Some changes to prepare for endian change for QUIC: 1) Make data reader/write be able to read/write…

net/quic/platform/api/quic_endian.h

Index: net/quic/platform/api/quic_endian.h
diff --git a/net/quic/platform/api/quic_endian.h b/net/quic/platform/api/quic_endian.h
index adf5c520a3042a111761968cb3702fccf3f7a257..474143fc43c2a5184bd5b22f242032a9e6d006f1 100644
--- a/net/quic/platform/api/quic_endian.h
+++ b/net/quic/platform/api/quic_endian.h
@@ -9,6 +9,11 @@
 
 namespace net {
 
+enum Endianness {
+  NETWORK_BYTE_ORDER,  // big endian
+  HOST_BYTE_ORDER      // little endian
+};
+
 // Provide utility functions that convert from/to network order (big endian)
 // to/from host order (can be either little or big endian depending on the
 // platform).