When I participate in Lync Meetings, I often hear the above sentence, when someone is presenting a PPT deck, the whiteboard, their desktop or a program. However, there is really no need for this, since the presenter (and the rest of the people in the meeting) can see from the roster or participant list, who can see the content. The color of the icon represents the modality status of the participant:
In Figure 1 below the first participant is currently sending both audio and content, but has not started video. The second participant is connected to audio and content, but has muted the microphone. The third and fourth participant are connected to both audio and content. However the fifth participant is connected to audio, but is not connected to the content.
Figure 1 Modality Status