Revert of Explicitly call SequenceToken's default constructor.

base/sequence_token_unittest.cc

 // Copyright 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/sequence_token.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 TEST(SequenceTokenTest, IsValid) {
   EXPECT_FALSE(SequenceToken().IsValid());
   EXPECT_TRUE(SequenceToken::Create().IsValid());
 }
 
 TEST(SequenceTokenTest, OperatorEquals) {
-  SequenceToken invalid_a;
-  SequenceToken invalid_b;
+  const SequenceToken invalid_a;
+  const SequenceToken invalid_b;
   const SequenceToken valid_a = SequenceToken::Create();
   const SequenceToken valid_b = SequenceToken::Create();
 
   EXPECT_FALSE(invalid_a == invalid_a);
   EXPECT_FALSE(invalid_a == invalid_b);
   EXPECT_FALSE(invalid_a == valid_a);
   EXPECT_FALSE(invalid_a == valid_b);
 
   EXPECT_FALSE(valid_a == invalid_a);
   EXPECT_FALSE(valid_a == invalid_b);
   EXPECT_EQ(valid_a, valid_a);
   EXPECT_FALSE(valid_a == valid_b);
 }
 
 TEST(SequenceTokenTest, OperatorNotEquals) {
-  SequenceToken invalid_a;
-  SequenceToken invalid_b;
+  const SequenceToken invalid_a;
+  const SequenceToken invalid_b;
   const SequenceToken valid_a = SequenceToken::Create();
   const SequenceToken valid_b = SequenceToken::Create();
 
   EXPECT_NE(invalid_a, invalid_a);
   EXPECT_NE(invalid_a, invalid_b);
   EXPECT_NE(invalid_a, valid_a);
   EXPECT_NE(invalid_a, valid_b);
 
   EXPECT_NE(valid_a, invalid_a);
   EXPECT_NE(valid_a, invalid_b);
@@ skipping 10 matching lines @@
     ScopedSetSequenceTokenForCurrentThread
         scoped_set_sequence_token_for_current_thread(token);
     EXPECT_TRUE(SequenceToken::GetForCurrentThread().IsValid());
     EXPECT_EQ(token, SequenceToken::GetForCurrentThread());
   }
 
   EXPECT_FALSE(SequenceToken::GetForCurrentThread().IsValid());
 }
 
 }  // namespace base