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

chrome/browser/download/save_package_file_picker.cc

Index: chrome/browser/download/save_package_file_picker.cc
diff --git a/chrome/browser/download/save_package_file_picker.cc b/chrome/browser/download/save_package_file_picker.cc
index 484e254a7a0634b6a2a36dbf979168c1228aac9d..00301d3549d07d5e7c59c24ab03a2a631d7fc737 100644
--- a/chrome/browser/download/save_package_file_picker.cc
+++ b/chrome/browser/download/save_package_file_picker.cc
@@ -142,11 +142,11 @@ SavePackageFilePicker::SavePackageFilePicker(
     // == 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;
@@ -187,7 +187,8 @@ SavePackageFilePicker::SavePackageFilePicker(
     // 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 .