workspacesView: Update visibily when gesture drag begins
When dragging the workspaces through the swipe gesture, all workspaces must be visible. WorkspacesView's _updateVisibility() method special-cases this and ensures that.
However, this method is only called when (1) going to the active workspace, and (2) when the gesture ends. That means, if there is any workspace hidden by the time a gesture starts, it is never shown!
Call _updateVisibility() on startTouchGesture() as well.
Related: #2969 (closed)
Edited by Georges Basile Stavracas Neto