Made root translation layer the root when using pinch virtual viewport.

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 f6acd868c5c06f7ca18cdb283d956a8117c33fae..084f8d553fd49f5400aec0744ac39f39f69b6371 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
@@ -877,6 +877,14 @@ void RenderLayerCompositor::updateDirectCompositingReasons(RenderLayer* layer)
     layer->setCompositingReasons(reasons, CompositingReasonComboAllDirectReasons);
 }
 
+void RenderLayerCompositor::setOverlayLayer(GraphicsLayer* layer)
+{
+    ASSERT(rootGraphicsLayer());
+
+    if (layer->parent() != m_overflowControlsHostLayer.get())
+        m_overflowControlsHostLayer->addChild(layer);
+}
+
 bool RenderLayerCompositor::canBeComposited(const RenderLayer* layer) const
 {
     // FIXME: We disable accelerated compositing for elements in a RenderFlowThread as it doesn't work properly.