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 909f4ffe8f4160049218f894d52e47a569ed226c..cad009a80ec12e630d6b9ea97754a239bb8145f3 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
@@ -912,6 +912,14 @@ 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.