ui: accessibility: remove -Wunused-function for Atk

ui: accessibility: remove -Wunused-function for Atk

Newer version of GLib define *get_instance_private symbols in
the G_DEFINE_TYPE macros. These symbols might be unused in cases
where a GObject class doesn't access its instances private data,
triggering -Wunused-function warnings.

BUG=504375
TEST=compile on linux with GLib >= 2.37

Committed: https://crrev.com/d080b42374a067e4c2d664027ca0952d5e2fb66e
Cr-Commit-Position: refs/heads/master@{#336576}

[llandwerlin-old, 2015-06-25 14:53:56]

lionel.g.landwerlin@intel.com changed reviewers:
+ dmazzoni@chromium.org

[llandwerlin-old, 2015-06-25 14:53:56]

Hi dmazzoni@, could you review this change?

[llandwerlin-old, 2015-06-26 16:48:46]

lionel.g.landwerlin@intel.com changed reviewers:
- dmazzoni@chromium.org

[llandwerlin-old, 2015-06-26 16:50:41]

lionel.g.landwerlin@intel.com changed reviewers:
+ dmazzoni@chromium.org

[Nico, 2015-06-29 02:06:01]

thakis@chromium.org changed reviewers:
+ thakis@chromium.org

[Nico, 2015-06-29 02:06:01]

Please add a comment explaining the flag (see
https://codereview.chromium.org/183223002/ for an example)

[llandwerlin-old, 2015-06-29 09:21:05]

On 2015/06/29 02:06:01, Nico wrote:
> Please add a comment explaining the flag (see
> https://codereview.chromium.org/183223002/ for an example)

Done.

[Nico, 2015-06-29 15:02:14]

lgtm

(ui/accessibility/BUILD.gn doesn't have either of these flags; once we switch to
gn I suppose this will be broken again)

[llandwerlin-old, 2015-06-29 15:33:58]

The CQ bit was checked by lionel.g.landwerlin@intel.com

[commit-bot: I haz the power, 2015-06-29 15:34:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1204293002/20001

[commit-bot: I haz the power, 2015-06-29 15:34:56]

The author lionel.g.landwerlin@intel.com has not signed Google Contributor
License Agreement. Please visit https://cla.developers.google.com to sign and
manage CLA.

[commit-bot: I haz the power, 2015-06-29 16:02:05]

The author lionel.g.landwerlin@intel.com has not signed Google Contributor
License Agreement. Please visit https://cla.developers.google.com to sign and
manage CLA.

[commit-bot: I haz the power, 2015-06-29 16:27:54]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-29 16:28:52]

Patchset 2 (id:??) landed as
https://crrev.com/d080b42374a067e4c2d664027ca0952d5e2fb66e
Cr-Commit-Position: refs/heads/master@{#336576}