Something is not clear to me regarding the action of the action.
Does the endpoint share (google + contacts or other signed glassware) get a timeline element with what it contains (html, attachment ...)?
Example:
If I have this item on my timeline ...
{ "menuItems": [{"action": "SHARE"}], "html": "<div>a beautiful HTML card</div>", "location": { "latitude": 40.702587, "timestamp": "2013-05-20T19:22:56.164600", "displayName": "KLOMPCHING GALLERY", "longitude": -73.98926, "address": "111 Front Street" }, "id": 42004, "isDeleted": false, "kind": "mirror#timelineItem" }
... and I click on share: will the sharing endpoint get the same JSON object?
source share