Add GesturePinchBegin/End events on Mac

Add GesturePinchBegin/End events on Mac

Because a single gesture (in NSEvent-speak) can contain multiple types
of sub-gestures (e.g, pinch and rotate), we do not get a begin/end
of the magnify-only part of the gesture. Work around this by saving
the NSEvent-gesture's beginning event, sending it (with the right type)
when the magnification begins, and sending an end event when the
gesture ends (only if a magnification event was sent).

BUG=451559
Committed: https://crrev.com/be0b14cb9955f2b4674e5f5f11755eb9f6276658
Cr-Commit-Position: refs/heads/master@{#314594}

[ccameron, 2015-01-29 23:04:45]

ccameron@chromium.org changed reviewers:
+ erikchen@chromium.org

[ccameron, 2015-01-29 23:04:45]

ptal (small change)

[erikchen, 2015-01-30 18:36:39]

lgtm

[ccameron, 2015-02-02 18:17:46]

The CQ bit was checked by ccameron@chromium.org

[commit-bot: I haz the power, 2015-02-02 18:18:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/886893002/1

[commit-bot: I haz the power, 2015-02-02 19:35:30]

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

[commit-bot: I haz the power, 2015-02-02 19:35:31]

Try jobs failed on following builders:
  mac_chromium_rel_ng on tryserver.chromium.mac
(http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[ccameron, 2015-02-02 22:37:59]

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

[ccameron, 2015-02-02 22:37:59]

Sky, could you stamp this?

erikchen, can you take a second look at the browser test changes.

[sky, 2015-02-03 00:39:26]

Can you pick a more local owner please? I'm not the best for mac changes. Maybe
avi?

[ccameron, 2015-02-03 00:46:35]

Last time I tried going with one of the *.mm OWNERS, that wasn't sufficient (see
https://codereview.chromium.org/811383003).

Adding avi (I'll try this again, maybe it was a fluke or transient condition).

[ccameron, 2015-02-03 23:37:28]

ccameron@chromium.org changed reviewers:
+ avi@chromium.org

[ccameron, 2015-02-03 23:37:29]

Adding avi for real this time.

[erikchen, 2015-02-03 23:39:01]

lgtm

[Avi (use Gerrit), 2015-02-04 00:22:23]

lgtm

[ccameron, 2015-02-04 00:23:25]

Thanks!

[ccameron, 2015-02-04 00:23:29]

The CQ bit was checked by ccameron@chromium.org

[commit-bot: I haz the power, 2015-02-04 00:24:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/886893002/20001

[commit-bot: I haz the power, 2015-02-04 00:30:02]

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

[commit-bot: I haz the power, 2015-02-04 00:30:03]

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

[ccameron, 2015-02-04 01:29:28]

New patchsets have been uploaded after l-g-t-m from
erikchen@chromium.org,avi@chromium.org

[ccameron, 2015-02-04 01:30:26]

sky, please review OWNERS change.

Added an OWNERS for this directory -- added the usual Mac files, plus erik (main
author of this stuff these days), and me.

[sky, 2015-02-04 18:05:45]

LGTM

[ccameron, 2015-02-04 18:06:30]

Thanks!

[ccameron, 2015-02-04 18:06:34]

The CQ bit was checked by ccameron@chromium.org

[commit-bot: I haz the power, 2015-02-04 18:07:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/886893002/40001

[commit-bot: I haz the power, 2015-02-04 18:45:18]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-02-04 18:46:27]

Patchset 3 (id:??) landed as
https://crrev.com/be0b14cb9955f2b4674e5f5f11755eb9f6276658
Cr-Commit-Position: refs/heads/master@{#314594}