Update from https://crrev.com/314320

base/i18n/file_util_icu.h

Index: base/i18n/file_util_icu.h
diff --git a/base/i18n/file_util_icu.h b/base/i18n/file_util_icu.h
index 7dd94cd9b06d2ab7ca3751a8b129dcf7237e4885..6d7f2ec6000a52971dafd89410ab7f63338af13a 100644
--- a/base/i18n/file_util_icu.h
+++ b/base/i18n/file_util_icu.h
@@ -18,13 +18,23 @@ namespace i18n {
 // param has the same restriction as that for ReplaceIllegalCharacters.
 BASE_I18N_EXPORT bool IsFilenameLegal(const string16& file_name);
 
-// Replaces characters in 'file_name' that are illegal for file names with
-// 'replace_char'. 'file_name' must not be a full or relative path, but just the
+// Replaces characters in |file_name| that are illegal for file names with
+// |replace_char|. |file_name| must not be a full or relative path, but just the
 // file name component (since slashes are considered illegal). Any leading or
-// trailing whitespace in 'file_name' is removed.
+// trailing whitespace or periods in |file_name| is also replaced with the
+// |replace_char|.
+//
 // Example:
-//   file_name == "bad:file*name?.txt", changed to: "bad-file-name-.txt" when
-//   'replace_char' is '-'.
+//   "bad:file*name?.txt" will be turned into "bad_file_name_.txt" when
+//   |replace_char| is '_'.
+//
+// Warning: Do not use this function as the sole means of sanitizing a filename.
+//   While the resulting filename itself would be legal, it doesn't necessarily
+//   mean that the file will behave safely. On Windows, certain reserved names
+//   refer to devices rather than files (E.g. LPT1), and some filenames could be
+//   interpreted as shell namespace extensions (E.g. Foo.{<GUID>}).
+//
+// TODO(asanka): Move full filename sanitization logic here.
 BASE_I18N_EXPORT void ReplaceIllegalCharactersInPath(
     FilePath::StringType* file_name,
     char replace_char);