Revert of Add a media scanner convenience class.

Revert of Add a media scanner convenience class. (patchset #1 id:1 of https://codereview.chromium.org/730353002/)

Reason for revert:
[Sheriff] Fails on cros and ozone:
http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/34127
http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Ozone%20Tests%20%282%29/builds/3852

Original issue's description:
> Add a media scanner convenience class.
>
> Create a new class that takes in a list of directories, recursively scans them for image and video files, and returns the resulting list.
>
> BUG=420680
> TEST=browser_test: FileManagerJsTest.MediaScannerTest
>
> Committed: https://crrev.com/340e607f73159216a2e7359c0a71170b9d4668f9
> Cr-Commit-Position: refs/heads/master@{#304582}

TBR=fukino@chromium.org,kenobi@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=420680
Committed: https://crrev.com/182392c4a2fdb0a82f967c271b781d027440fdd1
Cr-Commit-Position: refs/heads/master@{#304589}

[Michael Achenbach, 2014-11-18 12:26:20]

Created Revert of Add a media scanner convenience class.

[commit-bot: I haz the power, 2014-11-18 12:26:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/735013002/1

[commit-bot: I haz the power, 2014-11-18 12:27:18]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-18 12:28:14]

Patchset 1 (id:??) landed as
https://crrev.com/182392c4a2fdb0a82f967c271b781d027440fdd1
Cr-Commit-Position: refs/heads/master@{#304589}