Fix dir-locals handling for non-file buffers.

* lisp/files.el (dir-locals-collect-variables): Use default-directory
in place of the file name while working on non-file buffers, just
like hack-dir-local-variables already does.

Fixes: debbugs:19140

lisp/ChangeLog

@@ -6,6 +6,10 @@
 	* files.el (find-file-other-window, find-file-other-frame):
 	Use mapc instead of mapcar.  (Bug#18175)
+	* files.el (dir-locals-collect-variables): Use default-directory
+	in place of the file name while working on non-file buffers, just
+	like hack-dir-local-variables already does.  (Bug#19140)
+
 2015-01-17  Stefan Monnier  <monnier@iro.umontreal.ca>
 	* emacs-lisp/eieio-core.el (eieio--class-constructor): Rename from

lisp/files.el

@@ -3602,7 +3602,9 @@ Returns the new list."
   "Collect entries from CLASS-VARIABLES into VARIABLES.
 ROOT is the root directory of the project.
 Return the new variables list."
-  (let* ((file-name (buffer-file-name))
+  (let* ((file-name (or (buffer-file-name)
+			;; Handle non-file buffers, too.
+			(expand-file-name default-directory)))
 	 (sub-file-name (if file-name
                             ;; FIXME: Why not use file-relative-name?
 			    (substring file-name (length root)))))