[net] Cleanup filename_util and make it portable.

net/base/filename_util_unsafe.cc

Index: net/base/filename_util_unsafe.cc
diff --git a/net/base/filename_util_unsafe.cc b/net/base/filename_util_unsafe.cc
index 12e80dcf32d5f701b5525b413266451e9e662d36..18143838055e26e21bcbba93612c287f3db31055 100644
--- a/net/base/filename_util_unsafe.cc
+++ b/net/base/filename_util_unsafe.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/strings/string_util.h"
+#include "net/base/filename_util.h"
 #include "net/base/filename_util_internal.h"
 
 namespace {
@@ -18,12 +19,13 @@ const base::FilePath::CharType illegal_characters[] =
     FILE_PATH_LITERAL("\"*/:<>?\\\\|\001\002\003\004\005\006\007\010\011\012")
     FILE_PATH_LITERAL("\013\014\015\016\017\020\021\022\023\024\025\025\027");
 
-void ReplaceIllegalCharactersInPath(base::FilePath::StringType* file_name,
+void ReplaceIllegalCharactersInPath(base::FilePath* file_name,
                                     char replace_char) {
-  base::ReplaceChars(*file_name,
-                     illegal_characters,
+  base::FilePath::StringType filename_string = file_name->value();
+  base::ReplaceChars(filename_string, illegal_characters,
                      base::FilePath::StringType(1, replace_char),
-                     file_name);
+                     &filename_string);
+  *file_name = base::FilePath(filename_string);
 }
 
 }  // namespace
@@ -37,15 +39,14 @@ base::FilePath::StringType GenerateFileExtensionUnsafe(
     const std::string& suggested_name,
     const std::string& mime_type,
     const std::string& default_file_name) {
-  base::FilePath filepath =
-      GenerateFileNameImpl(url,
-                           content_disposition,
-                           referrer_charset,
-                           suggested_name,
-                           mime_type,
-                           default_file_name,
-                           base::Bind(&ReplaceIllegalCharactersInPath));
-  return filepath.Extension();
+  ExtensionGenerationOption extension_option = EXTENSION_OPTION_KEEP_EXISTING;
+  std::string unsafe_filename = SelectUnsafeDownloadFilename(
+      url, content_disposition, referrer_charset, suggested_name, mime_type,
+      default_file_name, &extension_option);
+  base::FilePath path = base::FilePath::FromUTF8Unsafe(unsafe_filename);
+  ReplaceIllegalCharactersInPath(&path, kReplacement);
+  EnsureSafeFilenameInternal(mime_type, extension_option, &path);
+  return path.Extension();
 }
 
 }  // namespace net