Introduce fileOperationUtil.

Introduce fileOperationUtil.

This CL introduces fileOperationUtil namespace and move/extracts some helper
methods from FileCopyManager to it.
This is preparation to move copyTo helper to it, so that moving the copyTo
from js-side to c++-side should be simpler task. The moving copyTo will be done
in following CLs.

BUG=246976
TEST=Ran browser_tests --gtest_filter="*FileSystemExtensionApiTest*:*FileManagerBrowserTest*" and tested manually.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=215854

[hidehiko, 2013-08-06 05:23:57]

Thank you for your review in advance,
- hidehiko

[mtomasz, 2013-08-06 05:34:02]

lgtm

[commit-bot: I haz the power, 2013-08-06 06:27:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hidehiko@chromium.org/22291004/1

[commit-bot: I haz the power, 2013-08-06 08:26:43]

Change committed as 215854