Multiline attribute values insert whitespace

[cjford]

The line break method implemented in #331 appears to insert a space inside the quoted string. Is this as designed, and if so, is there a reason behind it? It causes issues if the attribute value being broken up is a URL.

For example, this

link[rel="stylesheet" type="text/css" href="https://stylesheet-cdn.com/\
     this/is/a/quite/long/url/that/would/be/nice/to/split/up"]

results in a request to

https://stylesheetcdn.com/%20this/is/a/quite/long/url/that/would/be/nice/to/split/up

Same result if I remove the indentation on the second line.