Update from https://crrev.com/312398

base/stl_util_unittest.cc

 // Copyright 2012 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/stl_util.h"
 
 #include <set>
 
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 220 matching lines @@
   a3.insert(5);
 
   EXPECT_TRUE(STLIncludes<std::set<int> >(a1, a2));
   EXPECT_FALSE(STLIncludes<std::set<int> >(a1, a3));
   EXPECT_FALSE(STLIncludes<std::set<int> >(a2, a1));
   EXPECT_FALSE(STLIncludes<std::set<int> >(a2, a3));
   EXPECT_FALSE(STLIncludes<std::set<int> >(a3, a1));
   EXPECT_TRUE(STLIncludes<std::set<int> >(a3, a2));
 }
 
+TEST(StringAsArrayTest, Empty) {
+  std::string empty;
+  EXPECT_EQ(nullptr, string_as_array(&empty));
+}
+
+TEST(StringAsArrayTest, NullTerminated) {
+  // If any std::string implementation is not null-terminated, this should
+  // fail. All compilers we use return a null-terminated buffer, but please do
+  // not rely on this fact in your code.
+  std::string str("abcde");
+  str.resize(3);
+  EXPECT_STREQ("abc", string_as_array(&str));
+}
+
+TEST(StringAsArrayTest, WriteCopy) {
+  // With a COW implementation, this test will fail if
+  // string_as_array(&str) is implemented as
+  // const_cast<char*>(str->data()).
+  std::string s1("abc");
+  const std::string s2(s1);
+  string_as_array(&s1)[1] = 'x';
+  EXPECT_EQ("axc", s1);
+  EXPECT_EQ("abc", s2);
+}
+
 }  // namespace
 }  // namespace base