Use guest's existing GestureRecognizer instead of global one.

Use guest's existing GestureRecognizer instead of global one.

This makes touch events work in <webview>.
Otherwise GestureRecognizer starts sending event to bogus Window*, which
crashes the browser.

BUG=413017
Test=
In a touch enabled device, open a chrome app that has a <webview>.
e.g. https://chrome.google.com/webstore/detail/edggnmnajhcbhlnpjnogkjpghaikidaa
Try doing the following actions, none of them should crash the browser.
1. Tap on an input box, e.g. by going to http://www.google.com.
2. Scrolling a page should work.
3. Go to a page that has no touch handlers, you should be able to scroll the
page w/o problem.
3. Go to a page that has touch handlers (e.g. touchstart), you should be able
to scroll the page w/o problem.
4. Go to a page that has preventDefault() on touchstart event, you shouldn't
be able to scroll the page.

Committed: https://crrev.com/764ceed3b786f3e92fa39d547ae55b0082c0601e
Cr-Commit-Position: refs/heads/master@{#294971}

[lazyboy, 2014-09-15 23:05:52]

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

[lazyboy, 2014-09-15 23:05:52]

FYI, I'm trying to write interactive_ui_tests with EventGenerator, but so far no
luck. Touch events aren't working and I need to spend more time working on it.
Sending it for review as this fixes an m38 blocker. I will handle the test
separately.

[sky, 2014-09-15 23:19:53]

LGTM

[lazyboy, 2014-09-15 23:46:15]

The CQ bit was checked by lazyboy@chromium.org

[commit-bot: I haz the power, 2014-09-16 00:01:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/572763002/1

[commit-bot: I haz the power, 2014-09-16 02:06:04]

Committed patchset #1 (id:1) as 23af0c89aae3da4df8a2f3a371d3ecf046352873

[commit-bot: I haz the power, 2014-09-16 02:11:42]

Patchset 1 (id:??) landed as
https://crrev.com/764ceed3b786f3e92fa39d547ae55b0082c0601e
Cr-Commit-Position: refs/heads/master@{#294971}