Web Inspector: [Styles] Cannot visually set caret before the first CSS property name...

Web Inspector: [Styles] Cannot visually set caret before the first CSS property name character
https://bugs.webkit.org/show_bug.cgi?id=89869

Reviewed by Vsevolod Vlasov.

The issue was due to the "editbox" SPAN having a negative margin, thus the leftmost caret position was getting clipped
by a synthetic SPAN container added by the TextPrompt.

* inspector/front-end/elementsPanel.css:
(.styles-section .properties > li.child-editing .webkit-css-property):
(.styles-section .properties li.child-editing):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121150 268f45cc-cd09-0410-ab3c-d52691b4dbfc