Give blink a chance to consume ctrl+wheel events before zooming

Today chromium consumes all mouse wheel events when the control key is pressed for the purposes of browser zoom (except on MacOS).  With this change we give the web page a chance to get and consume the wheel event first, in case it wants to override the behavior.  This makes Chrome consistent with IE and Firefox on Windows.  See http://crbug.com/289887 and the linked chromium-dev thread for discussion.

Apparently there were no tests at all for this functionality.  I've added new unit tests at RenderWidgetHost and WebContents layers.

Depends on blink change http://src.chromium.org/viewvc/blink?view=rev&rev=168088

BUG=289887

Review URL: https://codereview.chromium.org/177213016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254559 0039d316-1c4b-4281-b951-d872f2087c98
9 files changed