Moves QuicTag typedefs, and QuicTag utility methods to quic_tag.{h,cc}. No behavior change.

net/quic/core/quic_utils_test.cc

Index: net/quic/core/quic_utils_test.cc
diff --git a/net/quic/core/quic_utils_test.cc b/net/quic/core/quic_utils_test.cc
index ca3df9bfbb8b56762f4a84eea2f49dab30982ddb..c9eca5e8cda7805eaecabcb7be6e593afc172b95 100644
--- a/net/quic/core/quic_utils_test.cc
+++ b/net/quic/core/quic_utils_test.cc
@@ -24,17 +24,6 @@ TEST(QuicUtilsTest, ErrorToString) {
   EXPECT_STREQ("QUIC_NO_ERROR", QuicUtils::ErrorToString(QUIC_NO_ERROR));
 }
 
-TEST(QuicUtilsTest, TagToString) {
-  EXPECT_EQ("SCFG", QuicUtils::TagToString(kSCFG));
-  EXPECT_EQ("SNO ", QuicUtils::TagToString(kServerNonceTag));
-  EXPECT_EQ("CRT ", QuicUtils::TagToString(kCertificateTag));
-  EXPECT_EQ("CHLO", QuicUtils::TagToString(MakeQuicTag('C', 'H', 'L', 'O')));
-  // A tag that contains a non-printing character will be printed as a decimal
-  // number.
-  EXPECT_EQ("525092931",
-            QuicUtils::TagToString(MakeQuicTag('C', 'H', 'L', '\x1f')));
-}
-
 TEST(QuicUtilsTest, ParseQuicConnectionOptions) {
   QuicTagVector empty_options = QuicUtils::ParseQuicConnectionOptions("");
   EXPECT_EQ(0ul, empty_options.size());