Linux: Fix drag/drop crash in WebCore::DragData::modifierKeyState (issue #875).

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk/cef1@1070 5089003a-bbd8-11dd-ad1f-f1f9622dbc98
Linux: Update the drag&drop implementation to match other platforms (issue #876).

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk/cef1@1074 5089003a-bbd8-11dd-ad1f-f1f9622dbc98