Remove most of WebDOMEvent and delete WebDOMMouseEvent.

Remove most of WebDOMEvent and delete WebDOMMouseEvent.

While content needs to create a few event types, it almost never needs
to read any data back off them. All of these getters are actually
dead code. I also noticed that WebDOMMouseEvent is dead and removed it.

Committed: https://crrev.com/3ade2f22f2a1a3118c5bef2daa9df79f10bab530
Cr-Commit-Position: refs/heads/master@{#353900}

[esprehn, 2015-10-13 21:47:01]

esprehn@chromium.org changed reviewers:
+ dglazkov@chromium.org, pdr@chromium.org

[esprehn, 2015-10-13 21:51:10]

The CQ bit was checked by esprehn@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-13 21:55:18]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1402023002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1402023002/1

[pdr., 2015-10-13 22:04:13]

lgtm

[esprehn, 2015-10-13 22:04:43]

The CQ bit was unchecked by esprehn@chromium.org

[esprehn, 2015-10-13 22:04:45]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2015-10-13 22:08:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1402023002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1402023002/1

[commit-bot: I haz the power, 2015-10-13 23:21:30]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-13 23:22:21]

Patchset 1 (id:??) landed as
https://crrev.com/3ade2f22f2a1a3118c5bef2daa9df79f10bab530
Cr-Commit-Position: refs/heads/master@{#353900}