Invalidate :default pseudo classes when a default button is added or removed.

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

Index: third_party/WebKit/Source/core/html/HTMLInputElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLInputElement.cpp b/third_party/WebKit/Source/core/html/HTMLInputElement.cpp
index 5b0c88c1637ab1d087f0011daee466c585d87bde..1a52b21e6db3ad6dc24f78a46ace39a749f65a1f 100644
--- a/third_party/WebKit/Source/core/html/HTMLInputElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLInputElement.cpp
@@ -475,6 +475,7 @@ void HTMLInputElement::updateType()
 
     bool didStoreValue = m_inputType->storesValueSeparateFromAttribute();
     bool didRespectHeightAndWidth = m_inputType->shouldRespectHeightAndWidthAttributes();
+    bool couldBeSuccessfulSubmitButton = canBeSuccessfulSubmitButton();
 
     m_inputTypeView->destroyShadowSubtree();
     lazyReattachIfAttached();
@@ -529,6 +530,8 @@ void HTMLInputElement::updateType()
     addToRadioButtonGroup();
 
     setNeedsValidityCheck();
+    if ((couldBeSuccessfulSubmitButton || canBeSuccessfulSubmitButton()) && formOwner() && inDocument())
+        formOwner()->invalidateDefaultButtonStyle();
     notifyFormStateChanged();
 }