Ensure that SSL YouTube URLs receive SSL embeds.

props adamsilverstein, Otto42, JayCC.
fixes #23149.

Built from https://develop.svn.wordpress.org/trunk@26978


git-svn-id: http://core.svn.wordpress.org/trunk@26855 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE: set the 'add_unload_trigger' option to false for the main editor. Prevents DOM problems in Firefox when reloading the page, see #24067.
Built from https://develop.svn.wordpress.org/trunk@26979


git-svn-id: http://core.svn.wordpress.org/trunk@26856 1a063a9b-81f0-0310-95a4-ce76da25c4cd