Bug 1033260 - [Messages] Contact suggestion list didn't dismiss when focus on subject and message input field

- Add one more Assimilation case when focus on subject field
You mean the recipient node content? I didn't plan to do that at first. Actually I just want to verify the assimilation is called, but the current structure could not be verified easily(assimilation function is wrapped by bind), so I verify the behavior in assimilation instead. And I didn't perform detailed assertion because we already did these in recipient assimilation unit test suite, but I could add more assertion here if you prefer.