[Android] Pass WebInputEvent by const ref when creating LatencyInfo

A raw WebInputEvent should never be constructed, as it's an abstract base
class masquerading as a POD struct.  Use a const ref WebInputEvent arg
to prevent this.

NOTRY=true

Review URL: https://codereview.chromium.org/155043002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249400 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249400