Add rudimentary support for page status indicators

Just hide them when opening the editor and show again afterwards. Will
need Parsoid for proper support.

Corresponding patch in core: I2389ff9a5332a2b1d033eb75f0946e5241cfaaf4.

Bug: 23796
Change-Id: I3ce5e7869be50dcd189ca24e2b3d7ebc62de4fc4
Merge "Add rudimentary support for page status indicators"