SECURITY: Prepend jsonp callback with comment

Mitigate CVE-2014-4671 for unpatched flash players

Bug: 68187
Change-Id: I2f46e623c1f541dbbafb6e8333e0929055098b15
SECURITY: Copy prevent-clickjacking between OutputPage and ParserOutput

Special page transclusion returns an OutputPage, whose metadata is
copied into the ParserOutput, and then later back into an OutputPage.
The "preventClickjacking" flag should be part of that metadata.

Bug: 65778
Change-Id: I17d2720fb94bb383a92059e5adbf6c16ee3e9ef4