RFR 9: MergedTabShiftTabTest sometimes time outs

[Jan Lahoda]

Hi,

The MergedTabShiftTabTest takes a long time and sometimes time outs on 
some machines. (Although on some others it takes <10s.) The test may be 
I/O intensive, so that may be the reason. The proposal here is to: a) 
split the test into two, to reduce the time spent in the test; b) give 
the probably longer part of the test higher timeout.

Webrev:
http://cr.openjdk.java.net/~jlahoda/8178035/webrev.00/

Thanks,
     Jan