Review request for 7124337: [macosx] FileDialog fails to select multiple files

[Dmitry Cherepanov]

Hello,

The fix enables support for multiple file selection in AWT FileDialog. 
The fix also provides ability to select files from different folders and 
for this reason, there are some changes to the shared code. I've tested 
the changes with native file dialogs on other platforms and I haven't 
found any problems.

http://cr.openjdk.java.net/~dcherepanov/7124337/webrev.0/

Thanks,
Dmitry