Remove the MouseMove handler for overlay scrollbars.

The code is crashing for unknown reasons.  Disable it for now so we
can push an Android release.  This feature shouldn't be doing anything
on Android touch devices.

We should re-enable once someone is able to own the feature.

BUG=326635

Review URL: https://codereview.chromium.org/112973009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240743 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240743