Move WriteFile and WriteFileDescriptor from file_util to base namespace.

components/policy/core/common/policy_loader_win_unittest.cc

Index: components/policy/core/common/policy_loader_win_unittest.cc
diff --git a/components/policy/core/common/policy_loader_win_unittest.cc b/components/policy/core/common/policy_loader_win_unittest.cc
index 3383d04ece5e7758faf60acc58a7bfc28c6e6c40..4b066ee942c8498e8d7866b9057d366b1a0d0326 100644
--- a/components/policy/core/common/policy_loader_win_unittest.cc
+++ b/components/policy/core/common/policy_loader_win_unittest.cc
@@ -468,7 +468,7 @@ void PRegTestHarness::SetUp() {
   base::win::SetDomainStateForTesting(false);
   ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
   preg_file_path_ = temp_dir_.path().Append(PolicyLoaderWin::kPRegFileName);
-  ASSERT_TRUE(file_util::WriteFile(preg_file_path_,
+  ASSERT_TRUE(base::WriteFile(preg_file_path_,
                                    preg_parser::kPRegFileHeader,
                                    arraysize(preg_parser::kPRegFileHeader)));