1 files changed, 66 insertions, 0 deletions
diff --git a/Source/WebCore/Modules/modern-media-controls/controls/scheduler.js b/Source/WebCore/Modules/modern-media-controls/controls/scheduler.js
new file mode 100644
index 000000000..f85beb037
--- /dev/null
+++ b/Source/WebCore/Modules/modern-media-controls/controls/scheduler.js
@@ -0,0 +1,66 @@
+
+const scheduler = new class
+{
+
+    constructor()
+    {
+        this._frameID = -1;
+        this._layoutCallbacks = new Set;
+    }
+
+    // Public
+
+    get hasScheduledLayoutCallbacks()
+    {
+        return this._frameID !== -1 || this._layoutCallbacks.size > 0;
+    }
+
+    scheduleLayout(callback)
+    {
+        if (typeof callback !== "function")
+            return;
+
+        this._layoutCallbacks.add(callback);
+        this._requestFrameIfNeeded();
+    }
+
+    unscheduleLayout(callback)
+    {
+        if (typeof callback !== "function")
+            return;
+
+        this._layoutCallbacks.delete(callback);
+    }
+
+    // Private
+
+    _requestFrameIfNeeded()
+    {
+        if (this._frameID === -1 && this._layoutCallbacks.size > 0)
+            this._frameID = window.requestAnimationFrame(this._frameDidFire.bind(this));
+    }
+
+    _frameDidFire()
+    {
+        if (typeof scheduler.frameWillFire === "function")
+            scheduler.frameWillFire();
+
+        this._layout();
+        this._frameID = -1;
+        this._requestFrameIfNeeded();
+
+        if (typeof scheduler.frameDidFire === "function")
+            scheduler.frameDidFire();
+    }
+
+    _layout()
+    {
+        // Layouts are not re-entrant.
+        const layoutCallbacks = this._layoutCallbacks;
+        this._layoutCallbacks = new Set;
+
+        for (let callback of layoutCallbacks)
+            callback();
+    }
+
+};