Fix character set used for dynamically loaded scripts.
Reviewed by Weinig, Dan and Alexey.
Fix for:
<rdar://problem/
5333163> Safari can not display the mouse over pop menu on ChinaTimes News site correctly.
<rdar://problem/
5530048> [Safari]? :Leopard9A576: The typed CH characters displays as garbage in Sina website after reloading the webpage.
<rdar://problem/
5416588> All menus for chinese IBM site have wrong encoding
Use the same logic to determine the charset for a script loaded dynamically
as we do for a statically loaded script.
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@28612
268f45cc-cd09-0410-ab3c-
d52691b4dbfc