Cleanup code that was used for verifying styling results for throttled animation flush in post traversal.

Now that we do process normal traversal even in the case of throttled animation
flush so that we don't need to do special handling for the case.

Note about the comment in has_current_styles():
the remaining animation hints is not caused by either this patch or the
previous patch in this patch series, it's been there in the first place, but
it should be fixed somehow later. See bug 1389675.

MozReview-Commit-ID: JojHufxNCiS

components/style/dom.rs

@@ -462,6 +462,28 @@ pub trait TElement : Eq + PartialEq + Debug + Hash + Sized + Copy + Clone +
         data.has_styles() && !data.restyle.hint.has_non_animation_invalidations()
     }
 
+    /// Returns whether the element's styles are up-to-date after traversal
+    /// (i.e. in post traversal).
+    fn has_current_styles(&self, data: &ElementData) -> bool {
+        if self.has_snapshot() && !self.handled_snapshot() {
+            return false;
+        }
+
+        data.has_styles() &&
+        // TODO(hiro): When an animating element moved into subtree of
+        // contenteditable element, there remains animation restyle hints in
+        // post traversal. It's generally harmless since the hints will be
+        // processed in a next styling but ideally it should be processed soon.
+        //
+        // Without this, we get failures in:
+        //   layout/style/crashtests/1383319.html
+        //   layout/style/crashtests/1383001.html
+        //
+        // https://bugzilla.mozilla.org/show_bug.cgi?id=1389675 tracks fixing
+        // this.
+        !data.restyle.hint.has_non_animation_invalidations()
+    }
+
     /// Flag that this element has a descendant for style processing.
     ///
     /// Only safe to call with exclusive access to the element.