[net] Cleanup filename_util and make it portable.

content/browser/web_contents/web_drag_source_mac.mm

Index: content/browser/web_contents/web_drag_source_mac.mm
diff --git a/content/browser/web_contents/web_drag_source_mac.mm b/content/browser/web_contents/web_drag_source_mac.mm
index 57e12a0b04ceb8575c9703a386726e8499f0a4c0..de66ebc1851202f7a6841f9a92a9f38099fbe9a7 100644
--- a/content/browser/web_contents/web_drag_source_mac.mm
+++ b/content/browser/web_contents/web_drag_source_mac.mm
@@ -69,12 +69,9 @@ base::FilePath GetFileNameFromDragData(const DropData& drop_data) {
   // Images without ALT text will only have a file extension so we need to
   // synthesize one from the provided extension and URL.
   if (file_name.empty()) {
-    // Retrieve the name from the URL.
-    base::string16 suggested_filename =
-        net::GetSuggestedFilename(drop_data.url, "", "", "", "", "");
-    const std::string extension = file_name.Extension();
-    file_name = FilePathFromFilename(suggested_filename);
-    file_name = file_name.ReplaceExtension(extension);
+    file_name =
+        net::GenerateFileName(drop_data.url, std::string(), std::string(),
+                              std::string(), std::string(), std::string());
   }
 
   return file_name;