Remove unnecessary DCHECK in TouchEventQueue handler notification

Remove unnecessary DCHECK in TouchEventQueue handler notification

Previously, the TouchEventQueue would flush itself when notified that
all touch handlers have been removed. As that is no longer the case,
remove the assert verifying that the queue is empty when notified that
a touch handler has been added.

BUG=406916
Committed: https://crrev.com/ce3cbf9560595152b9494ef51f109edd705abb04
Cr-Commit-Position: refs/heads/master@{#294711}

[jdduke (slow), 2014-09-12 21:52:24]

jdduke@chromium.org changed reviewers:
+ rbyers@chromium.org

[jdduke (slow), 2014-09-12 21:52:25]

rbyers@: PTAL. I missed this when removing the flush logic (and noticed it after
prompting from crbug.com/412723).

[Rick Byers, 2014-09-12 23:10:57]

lgtm

[jdduke (slow), 2014-09-12 23:22:14]

The CQ bit was checked by jdduke@chromium.org

[commit-bot: I haz the power, 2014-09-12 23:46:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/569793003/1

[commit-bot: I haz the power, 2014-09-13 01:01:41]

Committed patchset #1 (id:1) as 81cd3c110cfc031eecd3fc85a122b9bbca8bbafa

[commit-bot: I haz the power, 2014-09-13 01:09:30]

Patchset 1 (id:??) landed as
https://crrev.com/ce3cbf9560595152b9494ef51f109edd705abb04
Cr-Commit-Position: refs/heads/master@{#294711}