Avoid hacking on the case of a typename.

This allows me to mention the ImageData type without it being transformed to
"imagedata".  It may have some side-effects where we've been sloppy with
typenames elsewhere, but let me know if you see any, and I'll fix them.

Review URL: https://codereview.chromium.org/132203009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244332 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244332