Revert of DevTools: Parallelize trace messages serialization.

Revert of DevTools: Parallelize trace messages serialization. (patchset #7 id:140001 of https://codereview.chromium.org/750183008/)

Reason for revert:
Speculatively reverting this CL as it might be related to redness in the perf bots.

The new crashes on the bots all had this CL in their range, and the crashes are all related to MemoryError while receiving trace data.

(crbug.com/443398)

Feel free to reland if the revert does not fix the issue.

Original issue's description:
> DevTools: Parallelize trace messages serialization.
>
> Move serialization into a worker thread. As a result
> IO thread will be able to send messages to the browser.
>
> The original implementation did serialization on IO thread
> and was not able to send the messages because ipc had
> is_blocked_on_write_ = true and had no chance to check
> the actual state of the channel. So the messages were
> collected in output_queue. Also the messages could be quite
> big and could block the IO thread for a long time.
>
> BUG=
>
> Committed: https://crrev.com/d58e06aafd6572e681f9d30f313bf5393db9f2bc
> Cr-Commit-Position: refs/heads/master@{#308773}

TBR=nduca@chromium.org,pfeldman@chromium.org,caseq@chromium.org,yurys@chromium.org,wangxianzhu@chromium.org,skyostil@google.com,dsinclair@chromium.org,skyostil@chromium.org,loislo@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=443398
Committed: https://crrev.com/da5a86a1c9d8061eaec825dbd7296a7d608a1eff
Cr-Commit-Position: refs/heads/master@{#309257}

[fmeawad, 2014-12-19 21:01:02]

Created Revert of DevTools: Parallelize trace messages serialization.

[commit-bot: I haz the power, 2014-12-19 21:02:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/804083004/1

[commit-bot: I haz the power, 2014-12-19 21:03:37]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-19 21:04:23]

Patchset 1 (id:??) landed as
https://crrev.com/da5a86a1c9d8061eaec825dbd7296a7d608a1eff
Cr-Commit-Position: refs/heads/master@{#309257}