Web Inspector: CSS style declaration editor should ignore empty lines when determining prefix whitespace
https://bugs.webkit.org/show_bug.cgi?id=134704

Reviewed by Joseph Pecoraro.

When checking for zero-length prefix whitespace, completely empty lines are now ignored
as these lines are most often used for organizing rules into groups and often have their
whitespace removed due to trailing whitespace removal conventions.

* UserInterface/Views/CSSStyleDeclarationTextEditor.js:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170868 268f45cc-cd09-0410-ab3c-d52691b4dbfc