webapi: cookie-averse documents; HTMLElement.accessKeyLabel

Fixes two WPT files:

- /html/dom/documents/resource-metadata-management/document-cookie.html
  (4/5 -> 5/5, fully green): a cookie-averse document (one without a
  browsing context, e.g. createHTMLDocument) must read document.cookie
  as the empty string and silently ignore writes. Both accessors now
  no-op for documents that aren't a frame's active document.
- /html/dom/access-key-label.html (1/2 -> 2/2, fully green):
  HTMLElement.accessKeyLabel was missing. It reports an Alt+ chord for
  a valid single-character accesskey, like Chromium, and the empty
  string otherwise.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/browser/webapi/Document.zig

@@ -303,7 +303,18 @@ pub fn setDomain(self: *Document, value: []const u8) !void {
     try doc_frame.js.setOrigin(key);
 }
 
-pub fn getCookie(_: *Document, frame: *Frame) ![]const u8 {
+// A cookie-averse document (no browsing context: createHTMLDocument,
+// DOMParser, XHR documents) reads cookies as the empty string and ignores
+// writes.
+fn isCookieAverse(self: *const Document, frame: *const Frame) bool {
+    const doc_frame = self._frame orelse return true;
+    return doc_frame.document != self and frame.document != self;
+}
+
+pub fn getCookie(self: *Document, frame: *Frame) ![]const u8 {
+    if (self.isCookieAverse(frame)) {
+        return "";
+    }
     var buf: std.ArrayList(u8) = .empty;
     try frame._session.cookie_jar.forRequest(frame.url, buf.writer(frame.local_arena), .{
         .is_http = false,
@@ -312,7 +323,10 @@ pub fn getCookie(_: *Document, frame: *Frame) ![]const u8 {
     return buf.items;
 }
 
-pub fn setCookie(_: *Document, cookie_str: []const u8, frame: *Frame) ![]const u8 {
+pub fn setCookie(self: *Document, cookie_str: []const u8, frame: *Frame) ![]const u8 {
+    if (self.isCookieAverse(frame)) {
+        return cookie_str;
+    }
     // we use the cookie jar's allocator to parse the cookie because it
     // outlives the frame's arena.
     const Cookie = @import("storage/Cookie.zig");

src/browser/webapi/element/Html.zig

@@ -372,6 +372,17 @@ pub fn setTranslate(self: *HtmlElement, translate: bool, frame: *Frame) !void {
     try self.asElement().setAttributeSafe(comptime .wrap("translate"), .wrap(if (translate) "yes" else "no"), frame);
 }
 
+// accessKeyLabel: the UA-assigned shortcut for a valid (single character)
+// accesskey, or the empty string. We report an Alt+ chord like Chromium.
+pub fn getAccessKeyLabel(self: *HtmlElement, frame: *Frame) ![]const u8 {
+    const value = self.asElement().getAttributeSafe(comptime .wrap("accesskey")) orelse return "";
+    const codepoints = std.unicode.utf8CountCodepoints(value) catch return "";
+    if (codepoints != 1) {
+        return "";
+    }
+    return std.fmt.allocPrint(frame.call_arena, "Alt+{s}", .{value});
+}
+
 pub fn getPopover(self: *HtmlElement) ?[]const u8 {
     const s = popover.getState(self.asElement()) orelse return null;
     return @tagName(s);
@@ -1735,6 +1746,7 @@ pub const JsApi = struct {
     pub const dir = bridge.accessor(HtmlElement.getDir, HtmlElement.setDir, .{ .ce_reactions = true });
     pub const hidden = bridge.accessor(HtmlElement.getHidden, HtmlElement.setHidden, .{ .ce_reactions = true });
     pub const translate = bridge.accessor(HtmlElement.getTranslate, HtmlElement.setTranslate, .{ .ce_reactions = true });
+    pub const accessKeyLabel = bridge.accessor(HtmlElement.getAccessKeyLabel, null, .{});
     pub const popover = bridge.accessor(HtmlElement.getPopover, HtmlElement.setPopover, .{ .ce_reactions = true });
     pub const showPopover = bridge.function(HtmlElement.showPopover, .{});
     pub const hidePopover = bridge.function(HtmlElement.hidePopover, .{});