MMS: Fix the recipient box will not fit to screen width automatically

When tap new Message in the widget,the image button RecipientsPicker's
visibility is gone.The recipient box aligns to the left side of the image
button, so if the image button is gone, it will fit to screen width.

The visibility of image button RecipientsPicker set to visible.

CRs-Fixed: 526061

Change-Id: I068753ae961aab7fc9484cab180606b7f0481b57