Only composite opacity animations when already in compositing mode

Source/core/rendering/RenderLayerCompositor.cpp

Index: Source/core/rendering/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/RenderLayerCompositor.cpp b/Source/core/rendering/RenderLayerCompositor.cpp
index 0215204f02e0813b97bd4627c0eccb1f038a325c..f09423daf3e58180322098d96b0763f2bacef042 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -1677,7 +1677,10 @@ bool RenderLayerCompositor::requiresCompositingForAnimation(RenderObject* render
 {
     if (!(m_compositingTriggers & ChromeClient::AnimationTrigger))
         return false;
-    return renderer->animation().isRunningAcceleratableAnimationOnRenderer(renderer);
+
+    // FIXME: Remove this condition once force-compositing-mode is enabled on all platforms.
+    bool shouldAccelerateOpacity = inCompositingMode();
+    return renderer->animation().isRunningAcceleratableAnimationOnRenderer(renderer, shouldAccelerateOpacity);
 }
 
 bool RenderLayerCompositor::requiresCompositingForTransition(RenderObject* renderer) const