MiniBrowser doesn't support data URLs

MiniBrowser doesn't support data URLs
https://bugs.webkit.org/show_bug.cgi?id=135492

Reviewed by Simon Fraser.

* MiniBrowser/mac/BrowserWindowController.m:
(-[BrowserWindowController addProtocolIfNecessary:]):
Don't add http:// to data: URLs.

* MiniBrowser/mac/WK2BrowserWindowController.m:
(-[WK2BrowserWindowController fetch:]):
(-[WK2BrowserWindowController updateTextFieldFromURL:]):
Percent-escape the contents of the address field before trying to make a URL.
Percent-unescape the URL when displaying it in the address field.
This is not great, but trivial and good-enough-for-Minibrowser.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@171924 268f45cc-cd09-0410-ab3c-d52691b4dbfc