From 8d58197bf0609ef400e1cd28419a373d0ad199e4 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Mon, 2 Nov 2015 16:33:41 -0800
Subject: [PATCH] layout: Avoid flooding the compositor with animation state
 changes if there are no animations running and no new animations were added.

Avoids compositor jank during scroll.
---
 components/layout/animation.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/components/layout/animation.rs b/components/layout/animation.rs
index 99d257f38a4..27bf118bfda 100644
--- a/components/layout/animation.rs
+++ b/components/layout/animation.rs
@@ -58,6 +58,12 @@ pub fn update_animation_state(rw_data: &mut LayoutTaskData, pipeline_id: Pipelin
 
     let mut running_animations_hash = (*rw_data.running_animations).clone();
 
+    if running_animations_hash.is_empty() && new_running_animations.is_empty() {
+        // Nothing to do. Return early so we don't flood the compositor with
+        // `ChangeRunningAnimationsState` messages.
+        return
+    }
+
     // Expire old running animations.
     let now = clock_ticks::precise_time_s();
     let mut keys_to_remove = Vec::new();