DRT pasteboard object should return the correct pasteboard name.

DRT pasteboard object should return the correct pasteboard name.
https://bugs.webkit.org/show_bug.cgi?id=77260

Currently the name property always returns nil.
Adding a memeber variable to store the pasteboard name and return its
value from the name method instead of returning nil always.

Reviewed by Dan Bernstein.

* DumpRenderTree/mac/DumpRenderTreePasteboard.m:
(+[DumpRenderTreePasteboard _pasteboardWithName:]):
(-[LocalPasteboard initWithName:]):
(-[LocalPasteboard name]):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106171 268f45cc-cd09-0410-ab3c-d52691b4dbfc