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 ee8370585b465be36c7bd37a4f6c6d792ac4700d..8285e004336fecc8889d4b7a9e196197c57da291 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;