Delete the Layer Squashing runtime feature.

Source/core/rendering/compositing/RenderLayerCompositor.cpp

Index: Source/core/rendering/compositing/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/compositing/RenderLayerCompositor.cpp b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
index 473433309766013d54666e0509f6b6bb939a7e93..fbb1ae5cf0f9b2fe5e9cc33617079522a1f533d8 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
@@ -154,15 +154,6 @@ void RenderLayerCompositor::updateAcceleratedCompositingSettings()
         rootRenderLayer()->setNeedsCompositingInputsUpdate();
 }
 
-bool RenderLayerCompositor::layerSquashingEnabled() const
-{
-    if (!RuntimeEnabledFeatures::layerSquashingEnabled())
-        return false;
-    if (Settings* settings = m_renderView.document().settings())
-        return settings->layerSquashingEnabled();
-    return true;
-}
-
 bool RenderLayerCompositor::preferCompositingToLCDTextEnabled() const
 {
     return m_compositingReasonFinder.hasOverflowScrollTrigger();