[e] (0) Fix some typos or copypasta.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=21278
Affected topics: DOM APIs

git-svn-id: http://svn.whatwg.org/webapps@7830 340c8d12-0b0e-0410-8428-c7bf67bfef74
[e] (0) Change the variable name 'dialog' to 'subject' to avoid confusion. WARNING: THIS IS A RISKY CHANGE. (If anyone can carefully proof-read this diff that would be fantastic.)
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=20969
Affected topics: DOM APIs, HTML

git-svn-id: http://svn.whatwg.org/webapps@7831 340c8d12-0b0e-0410-8428-c7bf67bfef74