[fsp] [reupload] Enable the File System Provider API for extensions.

[fsp] [reupload] Enable the File System Provider API for extensions.

Previously, only apps were allowed to use this api, however most clients will
be actually written as extensions.

This patch has been once reverted due to a bug. See:
https://codereview.chromium.org/527663002/

TEST=browser_tests: *FileSystemProvider*Extension*
BUG=409487
Committed: https://crrev.com/c6986cbfb80ce8f995b8572090a53e0be1faf54c
Cr-Commit-Position: refs/heads/master@{#293285}

[mtomasz, 2014-09-04 00:59:11]

mtomasz@chromium.org changed reviewers:
+ benwells@chromium.org

[mtomasz, 2014-09-04 01:00:18]

@benwells: The only one change comparing to the previous (reverted) patch is:

RunPlatformAppTestWithFlags -> RunComponentExtensionTest

Since the new test running as an an extension, not an app.
That worked on Release, but not on Debug builds.

[benwells, 2014-09-04 01:32:57]

lgtm

[mtomasz, 2014-09-04 01:55:55]

The CQ bit was checked by mtomasz@chromium.org

[commit-bot: I haz the power, 2014-09-04 01:58:08]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/mtomasz@chromium.org/537153003/1

[commit-bot: I haz the power, 2014-09-04 03:29:15]

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

[commit-bot: I haz the power, 2014-09-04 03:29:16]

Try jobs failed on following builders:
  android_clang_dbg_recipe on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_clang_d...)

[mtomasz, 2014-09-04 09:25:08]

The CQ bit was checked by mtomasz@chromium.org

[commit-bot: I haz the power, 2014-09-04 09:25:57]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/mtomasz@chromium.org/537153003/1

[commit-bot: I haz the power, 2014-09-04 09:53:45]

Committed patchset #1 (id:1) as 985b07c8a1400a4a969b8856e04fa78bd3ac1bad

[commit-bot: I haz the power, 2014-09-10 03:30:55]

Patchset 1 (id:??) landed as
https://crrev.com/c6986cbfb80ce8f995b8572090a53e0be1faf54c
Cr-Commit-Position: refs/heads/master@{#293285}