Update some callers to use more direct ways of constructing IPAddress from well known literals.

net/quic/test_tools/quic_test_utils.cc

Index: net/quic/test_tools/quic_test_utils.cc
diff --git a/net/quic/test_tools/quic_test_utils.cc b/net/quic/test_tools/quic_test_utils.cc
index 1041569067a60245d42d7ac76eba2d7440187874..bc9fbc460422c7373e6e4ce20ad50d2da5b7c8d4 100644
--- a/net/quic/test_tools/quic_test_utils.cc
+++ b/net/quic/test_tools/quic_test_utils.cc
@@ -456,17 +456,15 @@ QuicVersion QuicVersionMin() {
 }
 
 IPAddress Loopback4() {
-  return IPAddress(127, 0, 0, 1);
+  return IPAddress::IPv4Localhost();
 }
 
 IPAddress Loopback6() {
-  IPAddress addr;
-  CHECK(addr.AssignFromIPLiteral("::1"));
-  return addr;
+  return IPAddress::IPv6Localhost();
 }
 
 IPAddress Any4() {
-  return IPAddress(0, 0, 0, 0);
+  return IPAddress::IPv4AllZeros();
 }
 
 void GenerateBody(string* body, int length) {