Refactor AppendToFile and WriteFileDescriptor

base/files/file_util_unittest.cc

 // Copyright (c) 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 "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <shellapi.h>
 #include <shlobj.h>
@@ skipping 1959 matching lines @@
   ASSERT_TRUE(CreateDirectory(data_dir));
 
   // Create a fresh, empty copy of this directory.
   if (PathExists(data_dir)) {
     ASSERT_TRUE(DeleteFile(data_dir, true));
   }
   ASSERT_TRUE(CreateDirectory(data_dir));
   FilePath foobar(data_dir.Append(FILE_PATH_LITERAL("foobar.txt")));
 
   std::string data("hello");
-  EXPECT_EQ(-1, AppendToFile(foobar, data.c_str(), data.length()));
+  EXPECT_FALSE(AppendToFile(foobar, data.c_str(), data.size()));
   EXPECT_EQ(static_cast<int>(data.length()),
             WriteFile(foobar, data.c_str(), data.length()));
-  EXPECT_EQ(static_cast<int>(data.length()),
-            AppendToFile(foobar, data.c_str(), data.length()));
+  EXPECT_TRUE(AppendToFile(foobar, data.c_str(), data.size()));
 
   const std::wstring read_content = ReadTextFile(foobar);
   EXPECT_EQ(L"hellohello", read_content);
 }
 
 TEST_F(FileUtilTest, ReadFile) {
   // Create a test file to be read.
   const std::string kTestData("The quick brown fox jumps over the lazy dog.");
   FilePath file_path =
       temp_dir_.path().Append(FILE_PATH_LITERAL("ReadFileTest"));
@@ skipping 592 matching lines @@
   // Trying to close it should crash. This is important for security.
   EXPECT_DEATH(CloseWithScopedFD(fds[1]), "");
 #endif
 }
 
 #endif  // defined(OS_POSIX)
 
 }  // namespace
 
 }  // namespace base