libservo: Move animation tracking from `WindowMethods` to delegates (#36400)

This changes removes animation tracking from the `WindowMethods` trait
and moves it to `ServoDelegate` and `WebViewDelegate`.

- Animation changes per-`WebView` are now triggered in the compositor
  only when the value is updated there, rather than right after ticking
  animations.
- Both `WebView` and `Servo` now expose an `animation()` method, so
  tracking animation state actually becomes unecessary in many cases,
  such as that of desktop servoshell, which can just read the value
  when the event loop spins.

Testing: No tests necessary as the API layer is still untested. Later,
tests will be added for the `WebView` API and this can be tested then.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/components/servo/webview_delegate.rs b/components/servo/webview_delegate.rs
index b631eae7404..ac3dc7a5152 100644
--- a/components/servo/webview_delegate.rs
+++ b/components/servo/webview_delegate.rs
@@ -375,6 +375,11 @@ pub trait WebViewDelegate {
     /// This [`WebView`] has either become focused or lost focus. Whether or not the
     /// [`WebView`] is focused can be accessed via [`WebView::focused`].
     fn notify_focus_changed(&self, _webview: WebView, _focused: bool) {}
+    /// This [`WebView`] has either started to animate or stopped animating. When a
+    /// [`WebView`] is animating, it is up to the embedding application ensure that
+    /// `Servo::spin_event_loop` is called at regular intervals in order to update the
+    /// painted contents of the [`WebView`].
+    fn notify_animating_changed(&self, _webview: WebView, _animating: bool) {}
     /// The `LoadStatus` of the currently loading or loaded page in this [`WebView`] has changed. The new
     /// status can accessed via [`WebView::load_status`].
     fn notify_load_status_changed(&self, _webview: WebView, _status: LoadStatus) {}