Refactor sinon helper to make it easier to use.

Refactor sinon helper to make it easier to use.

Previously unittests using sinon were required to use sinon.$setupStub
in order to typecheck correctly. It was usable only for the case when
the test wants to stub a single method, but not when a whole object is
stubbed. This CL gets rid of $setupStub and adds $testStub() function
that simply casts parameter to the TestStub type.

Committed: https://crrev.com/7ebfce1f9a43daef22f1d7601b4bbc031672bdc9
Cr-Commit-Position: refs/heads/master@{#320154}

[Sergey Ulanov, 2015-03-11 19:22:08]

sergeyu@chromium.org changed reviewers:
+ garykac@chromium.org, kelvinp@chromium.org

[Sergey Ulanov, 2015-03-11 19:46:22]

Patchset #2 (id:20001) has been deleted

[Sergey Ulanov, 2015-03-11 19:46:27]

Patchset #2 (id:40001) has been deleted

[garykac, 2015-03-11 20:20:04]

lgtm

[Sergey Ulanov, 2015-03-11 20:29:33]

The CQ bit was checked by sergeyu@chromium.org

[commit-bot: I haz the power, 2015-03-11 20:30:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1002553002/60001

[commit-bot: I haz the power, 2015-03-11 21:51:43]

Committed patchset #2 (id:60001)

[commit-bot: I haz the power, 2015-03-11 21:52:18]

Patchset 2 (id:??) landed as
https://crrev.com/7ebfce1f9a43daef22f1d7601b4bbc031672bdc9
Cr-Commit-Position: refs/heads/master@{#320154}