mash: Add a simple, temporary preferences store.

mash: Add a simple, temporary preferences store.

In the long run, we'll need a real solution to preferences, but for now,
we replace the implementation of PersistentPrefsStore with one that
writes JSON values to file on the mojo:filesystem. The current interface
isn't really a match made in heaven and it doesn't really deal with all
the complexity that we need to worry about (see 580652), but it's
reasonably sandboxed and will work for now.

BUG=557405, 580652
Committed: https://crrev.com/c0cbd1f4d7ad0374e1faa05a9531366a11ed7afd
Cr-Commit-Position: refs/heads/master@{#371086}

[Elliot Glaysher, 2016-01-22 21:19:37]

erg@chromium.org changed reviewers:
+ sky@chromium.org

[Elliot Glaysher, 2016-01-22 21:19:38]

The entire components/filesystem/public/cpp/prefs/ directory should be deleted
as soon as there's a real preferences implementation. I'm not entirely happy
with it, but without redesigning much larger parts of //base/prefs/, I suspect
this is the correct trade off of correctness vs effort.

Anything obvious that I'm missing?

[sky, 2016-01-22 22:21:13]

LGTM with the following fixed.

https://codereview.chromium.org/1624683002/diff/40001/components/filesystem/f...
File components/filesystem/file_impl.cc (right):

https://codereview.chromium.org/1624683002/diff/40001/components/filesystem/f...
components/filesystem/file_impl.cc:110: const size_t kBufferSize = 1 << 16;
Doesn't ReadAtCurrentPos take and return ints? In other words shouldn't
kBufferSize and len be ints?

https://codereview.chromium.org/1624683002/diff/40001/components/filesystem/p...
File components/filesystem/public/cpp/prefs/BUILD.gn (right):

https://codereview.chromium.org/1624683002/diff/40001/components/filesystem/p...
components/filesystem/public/cpp/prefs/BUILD.gn:5:
import("//mojo/public/tools/bindings/mojom.gni")
You probably don't need this import.

[Elliot Glaysher, 2016-01-22 22:32:41]

The CQ bit was checked by erg@chromium.org

[Elliot Glaysher, 2016-01-22 22:32:42]

The patchset sent to the CQ was uploaded after l-g-t-m from sky@chromium.org
Link to the patchset: https://codereview.chromium.org/1624683002/#ps60001
(title: "sky comments")

[commit-bot: I haz the power, 2016-01-22 22:35:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1624683002/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1624683002/60001

[commit-bot: I haz the power, 2016-01-22 23:49:09]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-01-22 23:50:25]

Description was changed from

==========
mash: Add a simple, temporary preferences store.

In the long run, we'll need a real solution to preferences, but for now,
we replace the implementation of PersistentPrefsStore with one that
writes JSON values to file on the mojo:filesystem. The current interface
isn't really a match made in heaven and it doesn't really deal with all
the complexity that we need to worry about (see 580652), but it's
reasonably sandboxed and will work for now.

BUG=557405, 580652
==========

to

==========
mash: Add a simple, temporary preferences store.

In the long run, we'll need a real solution to preferences, but for now,
we replace the implementation of PersistentPrefsStore with one that
writes JSON values to file on the mojo:filesystem. The current interface
isn't really a match made in heaven and it doesn't really deal with all
the complexity that we need to worry about (see 580652), but it's
reasonably sandboxed and will work for now.

BUG=557405, 580652

Committed: https://crrev.com/c0cbd1f4d7ad0374e1faa05a9531366a11ed7afd
Cr-Commit-Position: refs/heads/master@{#371086}
==========

[commit-bot: I haz the power, 2016-01-22 23:50:26]

Patchset 4 (id:??) landed as
https://crrev.com/c0cbd1f4d7ad0374e1faa05a9531366a11ed7afd
Cr-Commit-Position: refs/heads/master@{#371086}