UI/AppKit: Implement download directory selection

Ladybird/AppKit/Application/Application.mm

@@ -13,6 +13,7 @@
 #include <LibWebView/Application.h>
 #include <LibWebView/WebContentClient.h>
 #include <UI/LadybirdWebViewBridge.h>
+#include <Utilities/Conversions.h>
 
 #import <Application/Application.h>
 
@@ -24,6 +25,21 @@ namespace Ladybird {
 
 class ApplicationBridge : public WebView::Application {
     WEB_VIEW_APPLICATION(ApplicationBridge)
+
+private:
+    virtual Optional<ByteString> ask_user_for_download_folder() const override
+    {
+        auto* panel = [NSOpenPanel openPanel];
+        [panel setAllowsMultipleSelection:NO];
+        [panel setCanChooseDirectories:YES];
+        [panel setCanChooseFiles:NO];
+        [panel setMessage:@"Select download directory"];
+
+        if ([panel runModal] != NSModalResponseOK)
+            return {};
+
+        return Ladybird::ns_string_to_byte_string([[panel URL] path]);
+    }
 };
 
 ApplicationBridge::ApplicationBridge(Badge<WebView::Application>, Main::Arguments&)

Ladybird/AppKit/UI/LadybirdWebView.mm

@@ -1201,6 +1201,9 @@ static void copy_data_to_clipboard(StringView data, NSPasteboardType pasteboard_
                            }];
         })
         .when_rejected([self](auto const& error) {
+            if (error.is_errno() && error.code() == ECANCELED)
+                return;
+
             auto error_message = MUST(String::formatted("{}", error));
 
             auto* dialog = [[NSAlert alloc] init];