Revert of [GN] Don't rewrite files with the same contents

tools/gn/filesystem_utils.cc

Index: tools/gn/filesystem_utils.cc
diff --git a/tools/gn/filesystem_utils.cc b/tools/gn/filesystem_utils.cc
index 2ceca81677dbc68d0e041271ea9702ec1c3302c0..5905cdb9f1ec73749a03e15428d5109542712b22 100644
--- a/tools/gn/filesystem_utils.cc
+++ b/tools/gn/filesystem_utils.cc
@@ -687,86 +687,6 @@
   return toolchain_label.name() + "/";
 }
 
-bool ContentsEqual(const base::FilePath& file_path, const std::string& data) {
-  // Compare file and stream sizes first. Quick and will save us some time if
-  // they are different sizes.
-  int64_t file_size;
-  if (!base::GetFileSize(file_path, &file_size) ||
-      static_cast<size_t>(file_size) != data.size()) {
-    return false;
-  }
-
-  std::string file_data;
-  file_data.resize(file_size);
-  if (!base::ReadFileToString(file_path, &file_data))
-    return false;
-
-  return file_data == data;
-}
-
-bool WriteFileIfChanged(const base::FilePath& file_path,
-                        const std::string& data,
-                        Err* err) {
-  if (ContentsEqual(file_path, data))
-    return true;
-
-  // Create the directory if necessary.
-  if (!base::CreateDirectory(file_path.DirName())) {
-    if (err) {
-      *err =
-          Err(Location(), "Unable to create directory.",
-              "I was using \"" + FilePathToUTF8(file_path.DirName()) + "\".");
-    }
-    return false;
-  }
-
-  int size = static_cast<int>(data.size());
-  bool write_success = false;
-
-#if defined(OS_WIN)
-  // On Windows, provide a custom implementation of base::WriteFile. Sometimes
-  // the base version fails, especially on the bots. The guess is that Windows
-  // Defender or other antivirus programs still have the file open (after
-  // checking for the read) when the write happens immediately after. This
-  // version opens with FILE_SHARE_READ (normally not what you want when
-  // replacing the entire contents of the file) which lets us continue even if
-  // another program has the file open for reading. See http://crbug.com/468437
-  base::win::ScopedHandle file(::CreateFile(file_path.value().c_str(),
-                                            GENERIC_WRITE, FILE_SHARE_READ,
-                                            NULL, CREATE_ALWAYS, 0, NULL));
-  if (file.IsValid()) {
-    DWORD written;
-    BOOL result = ::WriteFile(file.Get(), data.c_str(), size, &written, NULL);
-    if (result) {
-      if (static_cast<int>(written) == size) {
-        write_success = true;
-      } else {
-        // Didn't write all the bytes.
-        LOG(ERROR) << "wrote" << written << " bytes to "
-                   << base::UTF16ToUTF8(file_path.value()) << " expected "
-                   << size;
-      }
-    } else {
-      // WriteFile failed.
-      PLOG(ERROR) << "writing file " << base::UTF16ToUTF8(file_path.value())
-                  << " failed";
-    }
-  } else {
-    PLOG(ERROR) << "CreateFile failed for path "
-                << base::UTF16ToUTF8(file_path.value());
-  }
-#else
-  write_success = base::WriteFile(file_path, data.c_str(), size) == size;
-#endif
-
-  if (!write_success && err) {
-    *err = Err(Location(), "Unable to write file.",
-               "I was writing \"" + FilePathToUTF8(file_path) + "\".");
-  }
-
-  return write_success;
-}
-
 SourceDir GetToolchainOutputDir(const Settings* settings) {
   return settings->toolchain_output_subdir().AsSourceDir(
       settings->build_settings());