Update WebInputEventFactory on Mac for pinch gesture support

Update WebInputEventFactory on Mac for pinch gesture support

WebInputEventFactory::gestureEvent was added a long time ago but is
not currently used.  Remove the existing unused code and update the
function to support creating GesturePinchUpdate events from Cocoa
NSEventTypeMagnify events.

BUG=289887
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=168482

[Rick Byers, 2014-03-04 21:49:00]

Adam, please review this little change to WebInputEventFactory::gestureEvent.

I talked to asvitkine@ who originally added this (for scroll rubber-banding
here: https://bugs.webkit.org/show_bug.cgi?id=65707) and he agreed removing it
was fine.  I couldn't find any existing callers and verified that Chrome on Mac
built and ran (with scroll rubberbanding) fine without this function, so this
change shouldn't affect anyone.

I'm happy to add a unit test, but when I started looking at it is was so trivial
as to seem a little silly (really just a second copy of the implementation -
creates a magnify event and makes sure we get a GesturePinchUpdate event from
it).

This will be used by: https://codereview.chromium.org/181723006/

Thanks,
   Rick

[abarth-chromium, 2014-03-04 22:08:01]

lgtm

[Rick Byers, 2014-03-04 22:09:40]

The CQ bit was checked by rbyers@chromium.org

[commit-bot: I haz the power, 2014-03-04 22:10:41]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rbyers@chromium.org/184983003/1

[commit-bot: I haz the power, 2014-03-05 14:56:34]

Change committed as 168482