Add a WebWidget::paintCompositedDeprecated.

public/web/WebWidget.h

Index: public/web/WebWidget.h
diff --git a/public/web/WebWidget.h b/public/web/WebWidget.h
index 0366479df6667e98b3d8b468347bed1786339bbb..456e20e8508fef75b2dbfec3cdc8e433d45bedac 100644
--- a/public/web/WebWidget.h
+++ b/public/web/WebWidget.h
@@ -122,6 +122,8 @@ public:
     // warranted before painting again).
     virtual void paint(WebCanvas*, const WebRect& viewPort, PaintOptions = ReadbackFromCompositorIfAvailable) { }
 
+    virtual void paintCompositedDeprecated(WebCanvas*, const WebRect&) { }
+
     // The caller is responsible for keeping the WebCompositeAndReadbackAsyncCallback
     // object alive until it is called.
     virtual bool compositeAndReadbackAsync(WebCompositeAndReadbackAsyncCallback*) { return false; }