A possible workaround is using Unicode Symbols:
Adapted code from this Google sample:
// Create a parent item and two children.
chrome.contextMenus.create({"title": "? Parent", "id": "parent"});
chrome.contextMenus.create(
{"title": "? Child 1", "parentId": "parent", "id": "child1"});
chrome.contextMenus.create(
{"title": "? Child 2", "parentId": "parent", "id": "child2"});
The submenu "Radio 1" behaves as a radio button, and it's defined with chrome.contextMenus.create({"title": "Radio 1", "type": "radio", "id": "radio1"});
This is just one of many pages of symbols:
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…