--- a/lisp/font-lock.el	Wed Feb 20 11:07:16 2013 +0100
+++ b/lisp/font-lock.el	Wed Feb 20 11:09:08 2013 +0100
@@ -1371,6 +1371,61 @@
   (font-lock-unfontify-region (point-min) (point-max))
   (set (make-local-variable 'font-lock-fontified) nil))
 
+(defvar font-lock-beg) (defvar font-lock-end)
+(defvar font-lock-extend-region-functions
+  '(font-lock-extend-region-wholelines
+    ;; This use of font-lock-multiline property is unreliable but is just
+    ;; a handy heuristic: in case you don't have a function that does
+    ;; /identification/ of multiline elements, you may still occasionally
+    ;; discover them by accident (or you may /identify/ them but not in all
+    ;; cases), in which case the font-lock-multiline property can help make
+    ;; sure you will properly *re*identify them during refontification.
+    font-lock-extend-region-multiline)
+  "Special hook run just before proceeding to fontify a region.
+This is used to allow major modes to help font-lock find safe buffer positions
+as beginning and end of the fontified region.  Its most common use is to solve
+the problem of /identification/ of multiline elements by providing a function
+that tries to find such elements and move the boundaries such that they do
+not fall in the middle of one.
+Each function is called with no argument; it is expected to adjust the
+dynamically bound variables `font-lock-beg' and `font-lock-end'; and return
+non-nil if it did make such an adjustment.
+These functions are run in turn repeatedly until they all return nil.
+Put first the functions more likely to cause a change and cheaper to compute.")
+;; Mark it as a special hook which doesn't use any global setting
+;; (i.e. doesn't obey the element t in the buffer-local value).
+(make-variable-buffer-local 'font-lock-extend-region-functions)
+
+(defun font-lock-extend-region-multiline ()
+  "Move fontification boundaries away from any `font-lock-multiline' property."
+  (let ((changed nil))
+    (when (and (> font-lock-beg (point-min))
+               (get-text-property (1- font-lock-beg) 'font-lock-multiline))
+      (setq changed t)
+      (setq font-lock-beg (or (previous-single-property-change
+                               font-lock-beg 'font-lock-multiline)
+                              (point-min))))
+    ;;
+    (when (get-text-property font-lock-end 'font-lock-multiline)
+      (setq changed t)
+      (setq font-lock-end (or (text-property-any font-lock-end (point-max)
+                                                 'font-lock-multiline nil)
+                              (point-max))))
+    changed))
+
+(defun font-lock-extend-region-wholelines ()
+  "Move fontification boundaries to beginning of lines."
+  (let ((changed nil))
+    (goto-char font-lock-beg)
+    (unless (bolp)
+      (setq changed t font-lock-beg (line-beginning-position)))
+    (goto-char font-lock-end)
+    (unless (bolp)
+      (unless (eq font-lock-end
+                  (setq font-lock-end (line-beginning-position 2)))
+        (setq changed t)))
+    changed))
+
 ;; This used to be `font-lock-fontify-region', and before that,
 ;; `font-lock-fontify-region' used to be the name used for what is now
 ;; `font-lock-fontify-syntactically-region'.
@@ -1383,6 +1438,19 @@
 	(progn
 	  ;; Use the fontification syntax table, if any.
 	  (if font-lock-syntax-table (set-syntax-table font-lock-syntax-table))
+	  (let ((funs font-lock-extend-region-functions)
+		(font-lock-beg beg)
+		(font-lock-end end))
+	    (while funs
+	      (setq funs (if (or (not (funcall (car funs)))
+				 (eq funs font-lock-extend-region-functions))
+			     (cdr funs)
+			   ;; If there's been a change, we should go through
+			   ;; the list again since this new position may
+			   ;; warrant a different answer from one of the fun
+			   ;; we've already seen.
+			   font-lock-extend-region-functions)))
+	    (setq beg font-lock-beg end font-lock-end))
 	  ;; Now do the fontification.
 	  (font-lock-unfontify-region beg end)
 	  (when font-lock-syntactic-keywords