datepicker: closing datepicker focuses input, breaking "open with focus"

[fxck]

https://stackblitz.com/edit/angular-material2-issue-b9oh8q?file=app%2Fapp.component.ts

1. focus input
2. select something, datepicker closes
3. (input focused) hit backspace couple of times
4. blur input
5. try to correct now nonsensical date
6. you are screwed, because input it not focused

it wasn't happening pre-beta.12, I would like to be able to turn this autofocus on close off again

cc @mmalerba @crisbeto

[mmalerba]

I think returning focus to where it started is the behavior most people will want. You should be able to get it to do something else by either blurring the active element or focusing the element you want focus to return to right before opening the datepicker. For example:

(focus)="$event.target.blur(); dp.open()"

[fxck]

..or we could add disableFocusRestore, it's three lines of code, I know you don't want to keep adding APIs, but I think this one is legit and has use cases

[mmalerba]

I'd prefer not to add a new API since it can be easily accomplished without it. I could see adding a note to the docs about it, which I can do when I get to updating the datepicker docs (next on my list after I finish input & select which I'm currently working on)