data-device: avoid duplicating data offer for the same client
weston_data_source_send_offer
is called to create a new data offer every time
when the seat focuses a surface. This patch will evite create a new data offer
for the same client for the same source, it fixes the bug of #376, where the
data device duplicates data offers thus it never been pasted to firefox.
Closes #376
Signed-off-by: xichen zhou sichem.zh@gmail.com
Edited by Daniel Stone