R1:5a723bff9177

Support synthetic submits from stacked actions

Summary: Fixes T10116.

Test Plan:
- Prior to patch: Control/Command + Enter submitted form but ignored actions.
- After patch: verifid command + enter submits actions.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10116

Differential Revision: https://secure.phabricator.com/D14991