Revert of Add ExtensionsTestBrowserContext class for test.

Revert of Add ExtensionsTestBrowserContext class for test. (https://codereview.chromium.org/355223002/)

Reason for revert:
This is breaking the Chrome OS valgrind bots:

http://build.chromium.org/p/chromium.memory.fyi/builders/Chromium%20OS%20(valgrind)(5)

For example:

http://build.chromium.org/p/chromium.memory.fyi/builders/Chromium%20OS%20%28valgrind%29%285%29/builds/28278

This is a problem with mixing tests that use TestingProfile and TestBrowserContext.  See crbug.com/395820

Original issue's description:
> Add ExtensionsTestBrowserContext class for test.
> and Use ExtensionTestBrowserContext for ImageLoader unittest.
> 
> ExtensionsTestBrowserContext class does 
> set TestExtensionsBrowserClient from constructor and
> call DestroyBrowserContextServices from destructor.
> 
> ExtensionTestBrowserContext will be used instead of TestingProfile.
> 
> R=yoz@chromium.org, rdevlin@chromium.org
> BUG=354046
> TEST=unit_tests --gtest_filter=ImageLoaderTest.DeleteExtensionWhileWaitingForCache
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=284330

TBR=jamescook@chromium.org
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=284567

[James Cook, 2014-07-21 22:23:02]

Created Revert of Add ExtensionsTestBrowserContext class for test.

[commit-bot: I haz the power, 2014-07-21 22:24:12]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jamescook@chromium.org/406093004/1

[commit-bot: I haz the power, 2014-07-21 22:24:12]

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

[commit-bot: I haz the power, 2014-07-21 22:24:13]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[James Cook, 2014-07-21 22:32:14]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2014-07-21 22:33:27]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jamescook@chromium.org/406093004/1

[Yoyo Zhou, 2014-07-21 22:44:08]

LGTM

[commit-bot: I haz the power, 2014-07-22 00:49:03]

Change committed as 284567

[limasdf, 2014-07-22 01:00:07]

Thank you very much for taking care of my previous patch. and I'm sorry that I
create a patch having problem.!

[James Cook, 2014-07-22 01:11:52]

On 2014/07/22 01:00:07, limasdf wrote:
> Thank you very much for taking care of my previous patch. and I'm sorry that I
> create a patch having problem.!

No problem. This stuff is very very tricky. I spent most of a day trying to
figure out what was wrong with my patch with these BrowserContext services.