Fixing crashes in layout tests when virtual-viewport is enabled.

Source/core/frame/PinchViewport.cpp

Index: Source/core/frame/PinchViewport.cpp
diff --git a/Source/core/frame/PinchViewport.cpp b/Source/core/frame/PinchViewport.cpp
index ca2d0d8688441e3e7dbe6c2192cf859602751c7b..f979f73ebbbf91c448f7076b6df20f4d997c046a 100644
--- a/Source/core/frame/PinchViewport.cpp
+++ b/Source/core/frame/PinchViewport.cpp
@@ -507,6 +507,8 @@ String PinchViewport::debugName(const GraphicsLayer* graphicsLayer)
         name =  "Overlay Scrollbar Horizontal Layer";
     } else if (graphicsLayer == m_overlayScrollbarVertical.get()) {
         name =  "Overlay Scrollbar Vertical Layer";
+    } else if (graphicsLayer == m_rootTransformLayer) {
+        name =  "Root Transform Layer";
     } else {
         ASSERT_NOT_REACHED();
     }