style: The 'all' property is not animatable.

Since it allows to animate display, which is not good.

This is a regression from:

  https://hg.mozilla.org/mozilla-central/rev/6884ba750aa3

Actually I wonder if the logic shouldn't be the other way around, i.e., a
shorthand is animatable if all the longhands are, not if just one.

In any case this rolls back to the previous behavior, should we do that, it
should be another bug.

Differential Revision: https://phabricator.services.mozilla.com/D14632

components/style/properties/data.py

@@ -388,12 +388,12 @@ class Shorthand(object):
             and allowed_in_keyframe_block != "False"
 
     def get_animatable(self):
-        animatable = False
+        if self.ident == "all":
+            return False
         for sub in self.sub_properties:
             if sub.animatable:
-                animatable = True
+                return True
-                break
+        return False
-        return animatable
 
     def get_transitionable(self):
         transitionable = False