[9] RFR for 8149737:JRE crash in com.sun.webkit.network.URLLoader.twkDidFinishLoading

[mikhail cherkasov]

Hi Guru, Kevin,

Please review the webrev :
  http://cr.openjdk.java.net/~mcherkas/8149737/webrev/

Crash occurs during the page destroy and still there is are some pending 
sub-resource from network.
I added a check for null, see line 814 in CachedResourceLoader.cpp to 
prevent crash.

JBS:
https://bugs.openjdk.java.net/browse/JDK-8149737

Thanks,
Mikhail.