Fix the initialization of PendingCallbacks in scheduled_test.

Fix the initialization of PendingCallbacks in scheduled_test.

This fixes a case where null was being passed to prefixLines, which also obviates the need for prefixLines to explicitly check for null.

R=amouravski@google.com

Committed: https://code.google.com/p/dart/source/detail?r=22648

[Andrei Mouravski, 2013-05-13 19:27:31]

Can you give me some context?

[nweiz, 2013-05-13 19:30:44]

On 2013/05/13 19:27:31, Andrei Mouravski wrote:
> Can you give me some context?

PendingCallback._ takes a thunk that returns the description of the pending
callback. The thunk was failing to actually return the string.

prefixLines was returning '' because it was getting passed the result of
PendingCallback.toString(), and that avoided a crash. It shouldn't have to
manually check for null, though, so that check was removed.

[Andrei Mouravski, 2013-05-13 19:53:07]

lgtm

You should move that context into the review description so it lives in
perpetuity.

[nweiz, 2013-05-13 20:10:05]

Committed patchset #1 manually as r22648 (presubmit successful).