Bug 1353628 - Part 3: Create PropertyAnimation for shorthands.

Therefore, we can start transitions on shorthand properties properly.

MozReview-Commit-ID: Ev2u2tEalnK

components/style/animation.rs

@@ -272,6 +272,15 @@ impl PropertyAnimation {
         let timing_function = box_style.transition_timing_function_mod(transition_index);
         let duration = box_style.transition_duration_mod(transition_index);
 
+        if transition_property.is_shorthand() {
+            return transition_property.longhands().iter().filter_map(|transition_property| {
+                PropertyAnimation::from_transition_property(*transition_property,
+                                                            timing_function,
+                                                            duration,
+                                                            old_style,
+                                                            new_style)
+            }).collect();
+        }
 
         if transition_property != TransitionProperty::All {
             if let Some(property_animation) =
@@ -305,6 +314,8 @@ impl PropertyAnimation {
                                 old_style: &ComputedValues,
                                 new_style: &ComputedValues)
                                 -> Option<PropertyAnimation> {
+        debug_assert!(!transition_property.is_shorthand() &&
+                      transition_property != TransitionProperty::All);
         let animated_property = AnimatedProperty::from_transition_property(&transition_property,
                                                                            old_style,
                                                                            new_style);

components/style/properties/helpers/animated_properties.mako.rs

@@ -158,6 +158,16 @@ impl TransitionProperty {
             _ => panic!("Not allowed to call longhands() for this TransitionProperty")
         }
     }
+
+    /// Returns true if this TransitionProperty is a shorthand.
+    pub fn is_shorthand(&self) -> bool {
+        match *self {
+            % for prop in data.shorthands_except_all():
+                TransitionProperty::${prop.camel_case} => true,
+            % endfor
+            _ => false
+        }
+    }
 }
 
 /// Returns true if this nsCSSPropertyID is one of the animatable properties.