Web Inspector: [Overview] Make "drag-to-move" feature more discoverable.
https://bugs.webkit.org/show_bug.cgi?id=113032

Reviewed by Pavel Feldman.

To move overview window user could drag-n-drop over
time "ribbon" on OverviewGrid.

This feature is hard to discover.

Setting "move" cursor will make this feature more discoverable.

* inspector/front-end/inspectorCommon.css:
Set "move" cursor to draggable area.
* inspector/front-end/OverviewGrid.js: Ditto.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146753 268f45cc-cd09-0410-ab3c-d52691b4dbfc