Show form validation message as a fallback tooltip.

third_party/WebKit/Source/core/html/HTMLInputElementTest.cpp

Index: third_party/WebKit/Source/core/html/HTMLInputElementTest.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLInputElementTest.cpp b/third_party/WebKit/Source/core/html/HTMLInputElementTest.cpp
index fb76476e4fe5de9e315a8f22379de0e386ad988e..c3dd8a6595e0f3d192cd20599e5022e7f3680080 100644
--- a/third_party/WebKit/Source/core/html/HTMLInputElementTest.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLInputElementTest.cpp
@@ -48,4 +48,16 @@ TEST(HTMLInputElementTest, NoAssertWhenMovedInNewDocument)
     document.body()->removeChild(document.body()->firstChild());
 }
 
+TEST(HTMLInputElementTest, DefaultToolTip)
+{
+    RefPtrWillBeRawPtr<Document> document = Document::create();
+    RefPtrWillBeRawPtr<HTMLHtmlElement> html = HTMLHtmlElement::create(*document);
+    html->appendChild(HTMLBodyElement::create(*document));
+    RefPtrWillBeRawPtr<HTMLInputElement> input = HTMLInputElement::create(*document, nullptr, false);
+    input->setBooleanAttribute(HTMLNames::requiredAttr, true);
+    toHTMLBodyElement(html->firstChild())->appendChild(input.get());
+    document->appendChild(html.release());
+    EXPECT_EQ("<<ValidationValueMissing>>", input->defaultToolTip());
+}
+
 } // namespace blink