Add FilePath::FinalExtension() to avoid double extensions (.tar.gz) for file selector

chrome/browser/download/save_package_file_picker.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 "chrome/browser/download/save_package_file_picker.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/i18n/file_util_icu.h"
 #include "base/metrics/histogram.h"
@@ skipping 124 matching lines @@
   // switching save-as file formats, and remove the flag/switch.
   if (ShouldSaveAsMHTML()) {
     default_extension_copy = FILE_PATH_LITERAL("mhtml");
     suggested_path_copy = suggested_path_copy.ReplaceExtension(
         default_extension_copy);
   } else if (can_save_as_complete_) {
     // NOTE: this branch will never run on chromeos because ShouldSaveAsHTML()
     // == can_save_as_complete_ on chromeos.
     bool add_extra_extension = false;
     base::FilePath::StringType extra_extension;
-    if (!suggested_path_copy.Extension().empty() &&
+    if (!suggested_path_copy.FinalExtension().empty() &&
         !suggested_path_copy.MatchesExtension(FILE_PATH_LITERAL(".htm")) &&
         !suggested_path_copy.MatchesExtension(FILE_PATH_LITERAL(".html"))) {
       add_extra_extension = true;
-      extra_extension = suggested_path_copy.Extension().substr(1);
+      extra_extension = suggested_path_copy.FinalExtension().substr(1);
     }
 
     static const size_t kNumberExtensions = arraysize(kIndexToIDS) - 1;
     file_type_info.extensions.resize(kNumberExtensions);
     file_type_info.extension_description_overrides.resize(kNumberExtensions);
 
     // Indices into kIndexToIDS are 1-based whereas indices into
     // file_type_info.extensions are 0-based. Hence the '-1's.
     // If you switch these resize()/direct-assignment patterns to push_back(),
     // then you risk breaking FileSelected()'s use of |index|.
@@ skipping 20 matching lines @@
     if (add_extra_extension) {
       file_type_info.extensions[kSelectFileCompleteIndex - 1].push_back(
           extra_extension);
     }
 
     file_type_info.include_all_files = false;
   } else {
     // The contents can not be saved as complete-HTML, so do not show the file
     // filters.
     file_type_info.extensions.resize(1);
-    file_type_info.extensions[0].push_back(suggested_path_copy.Extension());
+    file_type_info.extensions[0].push_back(
+        suggested_path_copy.FinalExtension());
 
     if (!file_type_info.extensions[0][0].empty()) {
       // Drop the .
       file_type_info.extensions[0][0].erase(0, 1);
     }
 
     file_type_info.include_all_files = true;
     file_type_index = 1;
   }
 
@@ skipping 77 matching lines @@
   }
 #endif
 
   callback_.Run(path_copy, save_type,
                 base::Bind(&OnSavePackageDownloadCreated));
 }
 
 void SavePackageFilePicker::FileSelectionCanceled(void* unused_params) {
   delete this;
 }