Add pixel readback to page popup

Source/web/WebPagePopupImpl.h

Index: Source/web/WebPagePopupImpl.h
diff --git a/Source/web/WebPagePopupImpl.h b/Source/web/WebPagePopupImpl.h
index 99f259ef5265f084d9ac233642da995938ac1097..ccae858dc51bb4a697c424f60f990a942dd47fec 100644
--- a/Source/web/WebPagePopupImpl.h
+++ b/Source/web/WebPagePopupImpl.h
@@ -63,6 +63,7 @@ public:
     void closePopup();
     WebWidgetClient* widgetClient() const { return m_widgetClient; }
     bool hasSamePopupClient(WebPagePopupImpl* other) { return other && m_popupClient == other->m_popupClient; }
+    virtual void compositeAndReadbackAsync(WebCompositeAndReadbackAsyncCallback*) OVERRIDE;
 
 private:
     // WebWidget functions
@@ -77,6 +78,7 @@ private:
     virtual void setFocus(bool) OVERRIDE;
     virtual bool isPagePopup() const OVERRIDE { return true; }
     virtual bool isAcceleratedCompositingActive() const OVERRIDE { return m_isAcceleratedCompositingActive; }
+    virtual WebWidgetClient* client() const OVERRIDE { return m_widgetClient; }
 
     // PageWidgetEventHandler functions
     virtual bool handleKeyEvent(const WebKeyboardEvent&) OVERRIDE;