Remove some unnecessary using directives from tests.

net/base/int128_unittest.cc

Index: net/base/int128_unittest.cc
diff --git a/net/base/int128_unittest.cc b/net/base/int128_unittest.cc
index 2d740d375d7d2ee95a67213f4717e1b1bcc9b2ce..9a9028978ab9b2c9ac532c7182cc5b25a717d43c 100644
--- a/net/base/int128_unittest.cc
+++ b/net/base/int128_unittest.cc
@@ -10,9 +10,9 @@
 #include "net/base/int128.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-using net::uint128;
-using net::uint128_pod;
-using net::kuint128max;
+namespace net {
+
+namespace test {
 
 TEST(Int128, AllTests) {
   uint128 zero(0);
@@ -264,3 +264,7 @@ TEST(Int128, AliasTests) {
   x3 += x3;
   EXPECT_EQ(x4, x3);
 }
+
+}  // namespace test
+
+}  // namespace net