Physical tab key not handled properly

[joaquimvila]

Steps to reproduce

1. Click on first input of showcase. Virtual keyboard appears just under it.
2. Press tab physical key (with physical keyboard). Focus moves to 2nd input and virtual keyboard also appears just under this 2nd input.
3. Click on showcase title. The focus is lost from 2nd input, but the virtual keyboard is still shown.
4. If another click is performed on showcase title, then the virtual keyboard disappears

Additional info
There's a "hack" in WDIO tests to bypass this situation. It consists of clicking twice on the showcase title to force the virtual keyboard to disappear. It is added on ShowcasePage::clickOnBackground() method, so fixing this issue would allow removing it.