Converted some extension browser tests into using event pages

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}

[oystein (OOO til 10th of July), 2015-05-27 18:36:34]

The CQ bit was checked by oysteine@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-05-27 18:38:18]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1108133002/40001

[commit-bot: I haz the power, 2015-05-27 19:43:31]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-05-27 19:43:32]

Dry run: This issue passed the CQ dry run.

[oystein (OOO til 10th of July), 2015-05-29 17:47:13]

Patchset #1 (id:1) has been deleted

[oystein (OOO til 10th of July), 2015-05-29 17:47:23]

Patchset #1 (id:20001) has been deleted

[oystein (OOO til 10th of July), 2015-05-29 17:47:30]

Patchset #1 (id:40001) has been deleted

[oystein (OOO til 10th of July), 2015-05-29 17:47:41]

The CQ bit was checked by oysteine@chromium.org to run a CQ dry run

[oystein (OOO til 10th of July), 2015-05-29 17:48:47]

oysteine@chromium.org changed reviewers:
+ kalman@chromium.org

[commit-bot: I haz the power, 2015-05-29 17:49:24]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1108133002/60001

[oystein (OOO til 10th of July), 2015-05-29 17:49:58]

kalman: This seems to be needed to be able to flip this thing on, or some tests
just time out. Whatcha think?

[commit-bot: I haz the power, 2015-05-29 19:59:53]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-05-29 19:59:54]

Dry run: This issue passed the CQ dry run.

[not at google - send to devlin, 2015-05-29 22:07:33]

lgtm

[oystein (OOO til 10th of July), 2015-05-29 22:07:48]

The CQ bit was checked by oysteine@chromium.org

[commit-bot: I haz the power, 2015-05-29 22:10:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1108133002/60001

[commit-bot: I haz the power, 2015-05-29 22:16:58]

Committed patchset #1 (id:60001)

[commit-bot: I haz the power, 2015-05-29 22:18:31]

Patchset 1 (id:??) landed as
https://crrev.com/1dc63af0201f5429133b814be52aab24f8d71f16
Cr-Commit-Position: refs/heads/master@{#332059}

[zhaoqin, 2015-06-01 03:36:28]

A revert of this CL (patchset #1 id:60001) has been created in
https://codereview.chromium.org/1159593004/ by zhaoqin@google.com.

The reason for reverting is: browser_tests ExtensionApiTest.AutotestPrivate
failed on MSan bot

BUG=494815.