Revert of Converted some extension browser tests into using event pages

Revert of Converted some extension browser tests into using event pages (patchset #1 id:60001 of https://codereview.chromium.org/1108133002/)

Reason for revert:
browser_tests ExtensionApiTest.AutotestPrivate failed on MSan bot

BUG=494815
Original issue's description:
> Converted some extension browser tests into using event pages, to fix some timeout issues when background pages have their DOM timers throttled.
>
> R=kalman
> BUG=
>
> Committed: https://crrev.com/1dc63af0201f5429133b814be52aab24f8d71f16
> Cr-Commit-Position: refs/heads/master@{#332059}

TBR=kalman@chromium.org,oysteine@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/cda8c938f06f9955ac895099d05a9db3b61f3ab5
Cr-Commit-Position: refs/heads/master@{#332159}

[zhaoqin, 2015-06-01 03:36:29]

Created Revert of Converted some extension browser tests into using event pages

[commit-bot: I haz the power, 2015-06-01 03:36:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1159593004/1

[commit-bot: I haz the power, 2015-06-01 03:37:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-01 03:37:53]

Patchset 1 (id:??) landed as
https://crrev.com/cda8c938f06f9955ac895099d05a9db3b61f3ab5
Cr-Commit-Position: refs/heads/master@{#332159}

[oystein (OOO til 10th of July), 2015-06-03 01:06:51]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1155333003/ by oysteine@chromium.org.

The reason for reverting is: Reverting the revert, the test failure was actually
fixed by this revert: https://codereview.chromium.org/1159353003.