Update is-valid flag upon resetting input elements.

Source/core/html/HTMLInputElement.cpp

Index: Source/core/html/HTMLInputElement.cpp
diff --git a/Source/core/html/HTMLInputElement.cpp b/Source/core/html/HTMLInputElement.cpp
index 27c7ce079ef56c5b53823aaccc73d1e0f5f4e998..80cda11bbe2e11fa7bf55f2af3aa5c9d85a2d3da 100644
--- a/Source/core/html/HTMLInputElement.cpp
+++ b/Source/core/html/HTMLInputElement.cpp
@@ -840,8 +840,10 @@ String HTMLInputElement::resultForDialogSubmit()
 
 void HTMLInputElement::resetImpl()
 {
-    if (m_inputType->storesValueSeparateFromAttribute())
+    if (m_inputType->storesValueSeparateFromAttribute()) {
         setValue(String());
+        setNeedsValidityCheck();
+    }
 
     setChecked(hasAttribute(checkedAttr));
     m_reflectsCheckedAttribute = true;