Reject calls when already in a call on mobile

[tOkeshu]

Automatically reject calls if we're already in another call on mobile.
Improve the UI to provide a meaningful warning for the caller.

[fqueze]

You don't need the audioOnly variable in here, so maybe move that test and early return just after the "var data = " ... line?

[fqueze]

Aren't most (of not all) of these rules duplicated with #callAnswer?

[fqueze]

Coding style: please fix the indent here.

[fqueze]

From IRC:
Here's a situation where the behavior isn't what I would expect (not sure if it existed before your changes or not).
A and B are on desktop (social api), C is on the mobile page. A attempts to call C (the accept/reject buttons appear on C's mobile page). Then B attempts to call C. B sees immediately the "caller is busy" message. C clicks "Reject".
Expected result: A sees the "call rejected" message.
Actual result: A still has the "Calling..." message

a random guess is that the reject message could be going to B instead of A when C clicks "reject"

Not sure what the conclusion of the IRC discussion was, so I'm pasting my IRC comments here for future reference.

I really like these changes otherwise :).

[fqueze]

This timer needs to be cancelled when the user closes the floating window by hand. Otherwise, it may execute if the user starts another call with the same contact; that's what caused the bug I mentioned at #37 (comment)

[fqueze]

• With 2 desktop (SocialAPI) clients A and B, if A calls B, B has an accept/reject floating window, then if A closes his floating window, B now has "The call has been closed" above the accept/reject buttons. The behavior I would expect would be: hide the accept/reject buttons, and display a "The call has been canceled" message.
• Clicking on the "reject" button of the floating window displays "The call has been closed" on the other side. Shouldn't it say "the call has been rejected"?