Disable stuck key detection on ChromeOS.

Disable stuck key detection on ChromeOS.

Since we can't rely on the modifier flags on ChromeOS, we can't use them
as a way to detect stuck modifier keys. This means that some actions
(including locking the screen) will result in Ctrl and Shift being stuck,
effectively regressing crbug.com/464534.

BUG=337509, 484329
Committed: https://crrev.com/feebce3f1423aa54b5fd4255ef6f747fbee58fa7
Cr-Commit-Position: refs/heads/master@{#330899}

[Jamie, 2015-05-20 00:09:21]

jamiewalch@chromium.org changed reviewers:
+ wez@chromium.org

[Jamie, 2015-05-20 00:09:22]

ptal

[Wez, 2015-05-20 18:48:45]

LGTM

What evidence do we have that the stuck modifier hack doesn't also break things
on non-CrOS platforms, though?

[Jamie, 2015-05-20 19:36:28]

The CQ bit was checked by jamiewalch@chromium.org

[commit-bot: I haz the power, 2015-05-20 19:37:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1145863002/1

[Jamie, 2015-05-20 19:42:37]

On 2015/05/20 18:48:45, Wez wrote:
> LGTM
> 
> What evidence do we have that the stuck modifier hack doesn't also break
things
> on non-CrOS platforms, though?

None; just lack of evidence that it does. The problem that it works around is
sufficiently annoying that I think it's worth keeping it unless we learn that
it's causing problems. In an ideal world, we would not see the Super key for
rewritten keys (bug 489881), and the Alt key remapping would be removed (bug
489879), so the modifiers would be set correctly for such events. If that
happens, we can remove this workaround.

[commit-bot: I haz the power, 2015-05-20 19:52:17]

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

[commit-bot: I haz the power, 2015-05-20 19:52:18]

Try jobs failed on following builders:
  linux_chromium_gn_chromeos_rel on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Jamie, 2015-05-21 01:12:08]

Rebase & fix compilation errors.

[Jamie, 2015-05-21 01:12:46]

The CQ bit was checked by jamiewalch@chromium.org

[Jamie, 2015-05-21 01:12:47]

The patchset sent to the CQ was uploaded after l-g-t-m from wez@chromium.org
Link to the patchset: https://codereview.chromium.org/1145863002/#ps20001
(title: "Rebase & fix compilation errors.")

[commit-bot: I haz the power, 2015-05-21 01:13:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1145863002/20001

[commit-bot: I haz the power, 2015-05-21 04:46:21]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-21 04:47:17]

Patchset 2 (id:??) landed as
https://crrev.com/feebce3f1423aa54b5fd4255ef6f747fbee58fa7
Cr-Commit-Position: refs/heads/master@{#330899}