Ubuntu – Layout change with Alt+Shift in Ubuntu 14.04 using Gnome 3.10

I know that many have asked that question before, but I have seen no one ask it for Ubuntu 14.04.

I have a test installation of Ubuntu 14.04 with GNOME 3.10 and I have also installed the Flashback sessions.

What I get is this:

Using either Unity or the Flashback Sessions, (Compiz and Metacity), I can change the change-layout combination to Alt+Shift and it works.

Just a note here using Unity:

If I go to:
System Settings–>Keyboard–>Shortcuts–>Typing–>Switch to next source, I can set it to Super+Space but NOT to Alt+Shift.

If I go to:
System Settings–>Keyboard–>Text Entry, I can set it to Alt+Shift L.

Now the first time I logged in to the GNOME Shell, the combination worked, but after a while it stopped.

I tried every setting available through the GUIs but none of them worked properly.

Right now I am in a state where the combination works everywhere but the GNOME-Shell.

If, working with GNOME-Shell, I go to:
System Settings–>Keyboard–>Shortcuts–>Typing–>Switch to next source, I can set it to Super+Space but NOT to Alt+Shift. Also even if I set to Super+Space it does not work.

If, working with GNOME-Shell, I go to:
System Settings–>Keyboard–>Layout Settings, everything is disabled so I have to go to –>Shortcut Settings where I can set it to Super+Space but NOT to Alt+Shift. Also even if I set to Super+Space it does not work. (it is actually the same with the above)

I have also tried to change it through GNOME-Tweak Tool but what it does it is that it actually changes the "Modifiers-only Switch to next Source" found in the above mentioned Keyboard settings, but it still does not do the trick.

In the GNOME-Shell the combination works only to change the layout from EN to GR. In order to change from GR to EN I have to use the mouse and go through the indicator on the top bar. Which by the way does not follow the current layout anyway.

Having faced this problem in Ubuntu 13.10 with GNOME I hoped that it would be fixed in 14.04.

Is there something that I am missing?

My OS Setup is Ubuntu 14.04 64-bit, and GNOME 3.10.4.
(Although strangely, when I go to the details on the System Settings it shows that I am using Ubuntu 13.10)

I have set up the system but made no modifications to it whatsoever through command line. I have only used GUI menus, and the only modifications I tried where the ones described above, regarding the change-layout key combination.