SourceURL comments for scripts having a name. 

sourceURL comment is now preferred script name for all scripts except 
for those with non zero start position (e.g. inline scripts in HTML). 


BUG=v8:2342
Review URL: https://codereview.chromium.org/10959038

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12576 ce2b1a6d-e550-0410-aec6-3dcde31c8c00