ash: Avoid treating screen resizes as user activity.

ash: Avoid treating screen resizes as user activity.

Tell UserActivityDetector to ignore mouse events received
soon after notification that displays have been changed.
Previously, the events were only ignored after making
requests to configure displays, but this appears to be
insufficient in some cases where configuration takes longer
than a second.

BUG=360634
Committed: https://crrev.com/2430b2a3cfbdf230c24b7ac05a19a07eb57cca90
Cr-Commit-Position: refs/heads/master@{#295482}

[Daniel Erat, 2014-09-16 15:19:02]

derat@chromium.org changed reviewers:
+ dnicoara@chromium.org

[Daniel Erat, 2014-09-16 15:19:03]

this is fairly gross, but the only alternative i can think of is increasing the
delay in ui/wm/core/user_activity_detector.cc beyond 1 second. i don't want to
do that because at some point i think we'll see a negative user impact from
this: we'll turn the screen off due to user inactivity and the user will move
the mouse/touchpad to try to wake the system up, but UserActivityDetector will
ignore the event since it arrived too soon after display reconfiguration.

[dnicoara, 2014-09-16 15:42:21]

lgtm

I did a bit of reading and I suspect that the mouse events are from cursor warps
as a result of display changes. On X11 that would look like a native event, so
I'm not sure if we can change that. The one thing I can think of is keep track
of cursor warps performed and ignore them in UserActivityDetector. Though this
is just a hunch.

[Daniel Erat, 2014-09-18 14:41:57]

putting in the CQ after adding a guard for a NULL UserActivityDetector (it looks
like we call this while Shell::Init() is still running... :-/)

[Daniel Erat, 2014-09-18 14:42:00]

The CQ bit was checked by derat@chromium.org

[commit-bot: I haz the power, 2014-09-18 14:43:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/570303003/20001

[commit-bot: I haz the power, 2014-09-18 16:40:56]

Committed patchset #2 (id:20001) as 98a76a10bdd3879c0946dacd88c28100fee81dc6

[commit-bot: I haz the power, 2014-09-18 16:41:29]

Patchset 2 (id:??) landed as
https://crrev.com/2430b2a3cfbdf230c24b7ac05a19a07eb57cca90
Cr-Commit-Position: refs/heads/master@{#295482}