Add "Please connect to a Wi-Fi network" string.

This string shows in a toast when the user tries to enable wireless
debugging while not connected to a Wi-Fi network.

Bug: 150139061

Test: make

Change-Id: I3d734e1edbbc3275d8365f3c168e8703d4861e13
(cherry picked from commit 8290c8edf9950d2f9a8a9c53aa8ffb466757d262)
1 file changed