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

tools/gn/filesystem_utils.h

Index: tools/gn/filesystem_utils.h
diff --git a/tools/gn/filesystem_utils.h b/tools/gn/filesystem_utils.h
index aaa08babde9e306ff82a0aca6b459ff30e170ee8..f64c00d751918238d685d49ef0701beab88bf62e 100644
--- a/tools/gn/filesystem_utils.h
+++ b/tools/gn/filesystem_utils.h
@@ -162,18 +162,6 @@
 // output. This will be the empty string to indicate that the toolchain outputs
 // go in the root build directory. Otherwise, the result will end in a slash.
 std::string GetOutputSubdirName(const Label& toolchain_label, bool is_default);
-
-// Returns true if the contents of the file and stream given are equal, false
-// otherwise.
-bool ContentsEqual(const base::FilePath& file_path, const std::string& data);
-
-// Writes given stream contents to the given file if it differs from existing
-// file contents. Returns true if new contents was successfully written or
-// existing file contents doesn't need updating, false on write error. |err| is
-// set on write error if not nullptr.
-bool WriteFileIfChanged(const base::FilePath& file_path,
-                        const std::string& data,
-                        Err* err);
 
 // -----------------------------------------------------------------------------