Revert "Revert of Fix update of validity cache value, so that it reflects the correct state of any …

Source/core/html/HTMLFormControlElement.cpp

Index: Source/core/html/HTMLFormControlElement.cpp
diff --git a/Source/core/html/HTMLFormControlElement.cpp b/Source/core/html/HTMLFormControlElement.cpp
index 4972a38a1bd7908f3be7cff35fbaaf736b078e9a..632f17c258c7bbaa3d6226c5dab49085f69d62c8 100644
--- a/Source/core/html/HTMLFormControlElement.cpp
+++ b/Source/core/html/HTMLFormControlElement.cpp
@@ -58,6 +58,7 @@ HTMLFormControlElement::HTMLFormControlElement(const QualifiedName& tagName, Doc
     , m_willValidateInitialized(false)
     , m_willValidate(true)
     , m_isValid(true)
+    , m_validityIsDirty(true)
     , m_wasChangedSinceLastFormControlChangeEvent(false)
     , m_wasFocusedByMouse(false)
 {
@@ -482,20 +483,25 @@ bool HTMLFormControlElement::checkValidity(WillBeHeapVector<RefPtrWillBeMember<F
 
 bool HTMLFormControlElement::isValidFormControlElement()
 {
-    // If the following assertion fails, setNeedsValidityCheck() is not called
-    // correctly when something which changes validity is updated.
-    ASSERT(m_isValid == valid());
+    if (m_validityIsDirty) {
+        m_isValid = valid();
+        m_validityIsDirty = false;
+    } else {
+        // If the following assertion fails, setNeedsValidityCheck() is not called
+        // correctly when something which changes validity is updated.
+        ASSERT(m_isValid == valid());
+    }
     return m_isValid;
 }
 
 void HTMLFormControlElement::setNeedsValidityCheck()
 {
-    bool newIsValid = valid();
-    if (willValidate() && newIsValid != m_isValid) {
+    if (willValidate()) {
         // Update style for pseudo classes such as :valid :invalid.
-        setNeedsStyleRecalc(SubtreeStyleChange);
+        if (valid() != m_isValid)

[tkent, 2014/09/25 05:35:55]

This is incorrect. Because setNeedsValidityCheck() can be called before all of
state changes are completed, valid() here may return an incorrect result, and we
might miss a necessary setNeedsStyleRecalc() call.

If style recalc cost is much larger than validation cost, a solution would be to
remove the validity lazy evaluation and the validity cache, and call valid()
every time.  This also can cause performance regression of
DOM/textarea-{dom,edit}.html performance tests.

[spartha, 2014/09/25 06:38:05]

As you suggest removing the validity cache should be fine. But actual issue is
with the style recalc. The tricky part is we need style recalc to update the
control's state, and we should avoid over doing it for performance. I cannot
think of a more reliable way to restrict the number style recalcs.

+            setNeedsStyleRecalc(SubtreeStyleChange);
+        m_validityIsDirty = true;
     }
-    m_isValid = newIsValid;
 
     // Updates only if this control already has a validation message.
     if (isValidationMessageVisible()) {