Fix Flaky EncryptedMediaTest

Fix Flaky EncryptedMediaTest

Tests are flaky as setMediaKeys() was not completing before the
"encrypted" event was generated. Change delays setting the video
source until setMediaKeys() completes.

BUG=444683
TEST=Failing tests run fine locally

Committed: https://crrev.com/37edfbac393c04549884ec15ce612a376a5be6ff
Cr-Commit-Position: refs/heads/master@{#309568}

[jrummell, 2014-12-23 00:33:35]

jrummell@chromium.org changed reviewers:
+ xhwang@chromium.org

[jrummell, 2014-12-23 00:33:35]

PTAL.

[xhwang, 2014-12-23 17:50:28]

Is the failure Linux only? If not, drop the "Linux" part in the CL title.

Otherwise LGTM!

[jrummell, 2014-12-23 17:58:57]

The CQ bit was checked by jrummell@chromium.org

[commit-bot: I haz the power, 2014-12-23 17:59:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/823743002/1

[commit-bot: I haz the power, 2014-12-23 18:57:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-23 18:59:22]

Patchset 1 (id:??) landed as
https://crrev.com/37edfbac393c04549884ec15ce612a376a5be6ff
Cr-Commit-Position: refs/heads/master@{#309568}

[jrummell, 2014-12-23 22:51:00]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/826603002/ by jrummell@chromium.org.

The reason for reverting is: This changes introduces a new problem that is
breaking the builds (e.g.
http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20MSan%20Brows....