Links to external stylesheets in the Styles sidebar should actually work. This bugfix should be rolled back once bug 58422 is fixed.
Patch to follow.
Created attachment 90028 [details]
[PATCH] Suggested fix
Attachment 90028 [details] did not pass style-queue:
Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'Source/WebCore/ChangeLog', u'Source/WebCor..." exit_code: 1
Source/WebCore/ChangeLog:8: Line contains tab character. [whitespace/tab] 
Total errors found: 1 in 1 files
If any of these errors are false positives, please file a bug against check-webkit-style.
Landing with a style fix.
Committed r84141: <http://trac.webkit.org/changeset/84141>