chrome/common/extensions/docs/examples/api/pageAction/set_icon/manifest.json

{
  "name": "Animated Page Action",
  "description": "This extension adds an animated browser action to the toolbar.",
  "version": "1.2",
  "background": {
    "page": "background.html"
  },
  "page_action": {
    "default_title": "First icon"
  },
  "manifest_version": 2
}