Move FilePathWatcher tests to base_unittests.

Move FilePathWatcher tests to base_unittests.

A long time ago, they had been moved to browser_tests. This was
because of the OS X implementation was flaky and caused hanging tests,
and the absence of robust test timeouts in unit tests resulted in the
entire test binary hanging.

Things have changed significantly meanwhile: The new test launcher
provides robust test timeout handling, and the OS X implementation has
been fixed. Hence, it's safe to move the test over to base_unittests.

BUG=chromium:78722
Committed: https://crrev.com/c2c9bb08b9683a1313f61b64614fa8e1e2c39785
Cr-Commit-Position: refs/heads/master@{#324680}

[Mattias Nissler (ping if slow), 2015-04-10 09:42:56]

mnissler@chromium.org changed reviewers:
+ pauljensen@chromium.org, rvargas@chromium.org

[pauljensen, 2015-04-10 11:09:20]

I'll let you fix the test failures before reviewing.

[Mattias Nissler (ping if slow), 2015-04-10 11:24:16]

On 2015/04/10 11:09:20, pauljensen wrote:
> I'll let you fix the test failures before reviewing.

Good point. The accidentally contains the line that I inserted to check whether
the test runner handles the hung test correctly. I'll also pull the android
fixes from your CL.

[Mattias Nissler (ping if slow), 2015-04-10 12:06:10]

OK, I've decide to make one step at a time to simplify things, so this CL just
moves the test to base_unittests without making any adjustments for Android.

Paul, my Android build environment isn't functional right now, so are you cool
with making the required Android adjustments?

[pauljensen, 2015-04-10 13:05:21]

> Paul, my Android build environment isn't functional right now, so are you cool
> with making the required Android adjustments?
Sure.

[pauljensen, 2015-04-10 13:07:18]

This CL lgtm.

[Mattias Nissler (ping if slow), 2015-04-10 13:58:31]

The CQ bit was checked by mnissler@chromium.org

[commit-bot: I haz the power, 2015-04-10 13:58:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1055703004/20001

[commit-bot: I haz the power, 2015-04-10 14:07:23]

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

[commit-bot: I haz the power, 2015-04-10 14:07:24]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[Mattias Nissler (ping if slow), 2015-04-10 14:15:19]

mnissler@chromium.org changed reviewers:
+ thestig@chromium.org

[Mattias Nissler (ping if slow), 2015-04-10 14:15:19]

+thestig@ for OWNERS review

[Lei Zhang, 2015-04-10 20:36:33]

The CQ bit was checked by thestig@chromium.org

[Lei Zhang, 2015-04-10 20:36:34]

lgtm

Woo, finally.

[commit-bot: I haz the power, 2015-04-10 20:37:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1055703004/20001

[commit-bot: I haz the power, 2015-04-10 21:03:04]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-10 21:04:46]

Patchset 2 (id:??) landed as
https://crrev.com/c2c9bb08b9683a1313f61b64614fa8e1e2c39785
Cr-Commit-Position: refs/heads/master@{#324680}