Remove pinch zoom handling from the browser process

Remove pinch zoom handling from the browser process

Pinch zoom is done by the renderer process now. Note that this leaves
the PreHandleGestureEvent in place, as most if not all instances of it
preventing gesture events are still desirable with the new pinch zoom
behavior.

BUG=451559
Committed: https://crrev.com/4907e06114a13ef908846f43b8332938c2d5f47f
Cr-Commit-Position: refs/heads/master@{#314925}

[ccameron, 2015-02-05 23:32:50]

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

[ccameron, 2015-02-05 23:32:50]

Entrails of the pinch change.

[Avi (use Gerrit), 2015-02-05 23:40:42]

lgtm

[ccameron, 2015-02-05 23:44:10]

Thanks!

[ccameron, 2015-02-05 23:44:13]

The CQ bit was checked by ccameron@chromium.org

[commit-bot: I haz the power, 2015-02-05 23:45:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/899283004/1

[commit-bot: I haz the power, 2015-02-06 00:39:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-06 00:40:51]

Patchset 1 (id:??) landed as
https://crrev.com/4907e06114a13ef908846f43b8332938c2d5f47f
Cr-Commit-Position: refs/heads/master@{#314925}