Revert of DevTools: Parallelize trace messages serialization.

Revert of DevTools: Parallelize trace messages serialization. (patchset #8 id:160001 of https://codereview.chromium.org/750183008/)

Reason for revert:
looks like it breaks image_decoding_measurements
http://build.chromium.org/p/chromium.perf/builders/Win%20XP%20Perf%20%283%29/builds/4285

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}
>
> Committed: https://crrev.com/e7d8d8b60e331469a7af4936e9fcc16630fb8fdf
> Cr-Commit-Position: refs/heads/master@{#315957}

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
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/d46e145dc210a5c71e3663de30a37373bca05872
Cr-Commit-Position: refs/heads/master@{#316038}

[loislo, 2015-02-12 20:10:47]

Created Revert of DevTools: Parallelize trace messages serialization.

[commit-bot: I haz the power, 2015-02-12 20:11:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/923693002/1

[commit-bot: I haz the power, 2015-02-12 20:12:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-12 20:13:09]

Patchset 1 (id:??) landed as
https://crrev.com/d46e145dc210a5c71e3663de30a37373bca05872
Cr-Commit-Position: refs/heads/master@{#316038}