Add base::UnguessableToken << operator

base/unguessable_token_unittest.cc

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/unguessable_token.h"
 
+#include <sstream>
 #include <type_traits>
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 void TestSmallerThanOperator(const UnguessableToken& a,
                              const UnguessableToken& b) {
   EXPECT_TRUE(a < b);
   EXPECT_FALSE(b < a);
@@ skipping 46 matching lines @@
 
   UnguessableToken Deserialized = UnguessableToken::Deserialize(high, low);
   EXPECT_EQ(token, Deserialized);
 }
 
 TEST(UnguessableTokenTest, VerifyToString) {
   UnguessableToken token = UnguessableToken::Deserialize(0x123, 0xABC);
   std::string expected = "(0000012300000ABC)";
 
   EXPECT_EQ(expected, token.ToString());
+
+  std::stringstream stream;
+  stream << token;
+  EXPECT_EQ(expected, stream.str());
 }
 
 TEST(UnguessableTokenTest, VerifySmallerThanOperator) {
   // Deserialize is used for testing purposes.
   // Use UnguessableToken::Create() in production code instead.
   {
     SCOPED_TRACE("a.low < b.low and a.high == b.high.");
     TestSmallerThanOperator(UnguessableToken::Deserialize(0, 1),
                             UnguessableToken::Deserialize(0, 5));
   }
@@ skipping 22 matching lines @@
             UnguessableTokenHash()(token));
 }
 
 TEST(UnguessableTokenTest, VerifyBasicUniqueness) {
   EXPECT_NE(UnguessableToken::Create(), UnguessableToken::Create());
 
   UnguessableToken token = UnguessableToken::Create();
   EXPECT_NE(token.GetHighForSerialization(), token.GetLowForSerialization());
 }
 }