Enable universal accelerated overflow scroll

Source/core/rendering/compositing/CompositingTriggers.h

Index: Source/core/rendering/compositing/CompositingTriggers.h
diff --git a/Source/core/rendering/compositing/CompositingTriggers.h b/Source/core/rendering/compositing/CompositingTriggers.h
index f3694c917e91d52901bcfa64051bfba8affad9b9..7b788f5ef3e32d86b3bb0f258120b5314d9e03c6 100644
--- a/Source/core/rendering/compositing/CompositingTriggers.h
+++ b/Source/core/rendering/compositing/CompositingTriggers.h
@@ -33,10 +33,14 @@ enum CompositingTrigger {
     FilterTrigger = 1 << 5,
     ScrollableInnerFrameTrigger = 1 << 6,
     GPURasterizationTrigger = 1 << 7,
+
     // FIXME: This is a temporary trigger for enabling the old, opt-in path for
     // accelerated overflow scroll. It should be removed once the "universal"
     // path is ready (crbug.com/254111).
+    // Currently there is no way to enable this trigger, which means we can
+    // remove it once we're confident in the current codepaths.
     LegacyOverflowScrollTrigger = 1 << 8,
+
     OverflowScrollTrigger = 1 << 9,
     ViewportConstrainedPositionedTrigger = 1 << 10,
     AllCompositingTriggers = 0xFFFFFFFF,