Use page popup pixel readback for calendar-picker-appearance.html

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index c9ca40a569f60048688a9fd98dd7e5f6944bcb0d..9c0e93fd88a0edc7dbdcdedb48d5998df4ee0ed6 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -1596,6 +1596,11 @@ void WebViewImpl::closePagePopup(PagePopup* popup)
     m_pagePopup = nullptr;
 }
 
+LocalDOMWindow* WebViewImpl::pagePopupWindow()
+{
+    return m_pagePopup ? m_pagePopup->window() : nullptr;
+}
+
 Frame* WebViewImpl::focusedCoreFrame() const
 {
     return m_page ? m_page->focusController().focusedOrMainFrame() : 0;