Revert of ServiceWorker: Introduce SWMessageSender in order to mock IPC messaging

Revert of ServiceWorker: Introduce SWMessageSender in order to mock IPC messaging (patchset #3 id:120001 of https://codereview.chromium.org/1011643002/)

Reason for revert:
Decided to take a different way to mock IPC messaging.
See review comments on the original CL for more details.

Original issue's description:
> ServiceWorker: Introduce SWMessageSender in order to mock IPC messaging
>
> This CL introduces ServiceWorkerMessageSender that is a thin wrapper
> of ThreadSafeSender so that unittests can inject a mock sender, and
> adds some unittests related to reference counting using the mock.
>
> BUG=452403
> TEST=content_unittests --gtest_filter=ServiceWorkerDispatcherTest.*
>
> Committed: https://crrev.com/4d44fa9f7fb3d97b916781a6051ed4dcc69c3668
> Cr-Commit-Position: refs/heads/master@{#320885}

TBR=ksakamoto@chromium.org
BUG=452403
Committed: https://crrev.com/5279a9fe65fbb014a99c3f9d6fdc860a59b952cc
Cr-Commit-Position: refs/heads/master@{#321080}

[nhiroki, 2015-03-18 02:21:06]

Created Revert of ServiceWorker: Introduce SWMessageSender in order to mock IPC
messaging

[nhiroki, 2015-03-18 04:05:07]

Patchset #2 (id:300001) has been deleted

[nhiroki, 2015-03-18 04:09:36]

The CQ bit was checked by nhiroki@chromium.org

[commit-bot: I haz the power, 2015-03-18 04:09:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1002393005/320001

[commit-bot: I haz the power, 2015-03-18 05:34:13]

Committed patchset #2 (id:320001)

[commit-bot: I haz the power, 2015-03-18 05:35:03]

Patchset 2 (id:??) landed as
https://crrev.com/5279a9fe65fbb014a99c3f9d6fdc860a59b952cc
Cr-Commit-Position: refs/heads/master@{#321080}