PopupMenuImpl should get menu items via PopupMenuClient.

Source/web/ExternalPopupMenuTest.cpp

Index: Source/web/ExternalPopupMenuTest.cpp
diff --git a/Source/web/ExternalPopupMenuTest.cpp b/Source/web/ExternalPopupMenuTest.cpp
index 3a9e9175a24d7bfa2355dd2c23eae87604f4b5a3..b3ab7fa2c83a3fabd81c9586cc762207dd82434a 100644
--- a/Source/web/ExternalPopupMenuTest.cpp
+++ b/Source/web/ExternalPopupMenuTest.cpp
@@ -36,6 +36,7 @@ public:
     void selectionChanged(unsigned listIndex, bool fireEvents = true) override { }
     void selectionCleared() override { }
 
+    Element& itemElement(unsigned listIndex) const override { return *m_ownerElement->listItems()[listIndex]; }
     String itemText(unsigned listIndex) const override { return emptyString(); }
     String itemToolTip(unsigned listIndex) const override { return emptyString(); }
     String itemAccessibilityText(unsigned listIndex) const override { return emptyString(); }
@@ -54,7 +55,6 @@ public:
     bool multiple() const override { return false; }
     IntRect elementRectRelativeToViewport() const override { return IntRect(); }
     Element& ownerElement() const override { return *m_ownerElement; }
-    const ComputedStyle* computedStyleForItem(Element& element) const override { return nullptr; }
     const ComputedStyle* computedStyleForItem(unsigned listIndex) const override
     {
         Element* element = m_ownerElement->listItems()[listIndex];