Fix crash in WebAXObject::showContextMenu

third_party/WebKit/Source/web/WebAXObject.cpp

Index: third_party/WebKit/Source/web/WebAXObject.cpp
diff --git a/third_party/WebKit/Source/web/WebAXObject.cpp b/third_party/WebKit/Source/web/WebAXObject.cpp
index 05c7c8b40f5531099fe31a85354349d16bb46d8e..c80ceb5a79ad0b4bc4ebc982d3747983e6a3d657 100644
--- a/third_party/WebKit/Source/web/WebAXObject.cpp
+++ b/third_party/WebKit/Source/web/WebAXObject.cpp
@@ -972,9 +972,13 @@ void WebAXObject::showContextMenu() const
     Element* element = nullptr;
     if (node->isElementNode()) {
         element = toElement(node);
+    } else if (node->isDocumentNode()) {
+        element = node->document().documentElement();
     } else {
         node->updateDistribution();
         ContainerNode* parent = FlatTreeTraversal::parent(*node);
+        if (!parent)
+            return;
         ASSERT_WITH_SECURITY_IMPLICATION(parent->isElementNode());
         element = toElement(parent);
     }