[Slimming Paint] Paint the inspector overlay with GraphicsLayer DisplayList.

Source/platform/graphics/paint/DisplayItem.cpp

Index: Source/platform/graphics/paint/DisplayItem.cpp
diff --git a/Source/platform/graphics/paint/DisplayItem.cpp b/Source/platform/graphics/paint/DisplayItem.cpp
index 9f482fd2d6cdae24f891077fcf44354c43793826..41b14bb8fd85d83b6f2628422150a8b5622cad20 100644
--- a/Source/platform/graphics/paint/DisplayItem.cpp
+++ b/Source/platform/graphics/paint/DisplayItem.cpp
@@ -56,6 +56,7 @@ static WTF::String drawingTypeAsDebugString(DisplayItem::Type type)
     case DisplayItem::VideoBitmap: return "DrawingVideoBitmap";
     case DisplayItem::ViewBackground: return "DrawingViewBackground";
     case DisplayItem::DebugRedFill: return "DrawingDebugRedFill";
+    case DisplayItem::PageOverlay: return "PageOverlay";
     default:
         ASSERT_NOT_REACHED();
         return "Unknown";