RFR 8241078: OOM error parsing HTML with large Tag text

[Prasanta Sadhukhan]

Hi All,

Please review a fix for an issue where it is seen that OOM errors 
generated when parsing HTML files with large <pre> tagtext.

This is because of fix done in JDK-8173123 where the entire data array 
was copied again and again, insteadof the range specified via offset.

Fix is to use the offset in array copying to only copy the range specified

Bug: https://bugs.openjdk.java.net/browse/JDK-8241078

webrev: http://cr.openjdk.java.net/~psadhukhan/8241078/webrev.0/

All javax/swing/text/html and javax/swing/text/DefaultStyleDocument 
jtreg test still pass after this change.

Regards
Prasanta